I haven't read the book in question, but having looked at the chapter you are referring to, I can provide some general answers. Our regional expert /u/Kochevnik81 might be able to provide more details as well.

EDIT 3: Also, just to note, the alphabet in question is not the "New Turkish Alphabet", but instead the "New Turkic Alphabet", Turkic being the family of languages (to which Turkish also belongs) spoken by most of the indigenous peoples of Central Asia.

Pynchon is mostly true to historical fact in general terms, even though he is using somewhat outdated terminology which might make things confusing for a modern reader (more on that later). Then there is an overt Orientalist angle of his writing that does not exactly paint the most accurate picture of Central Asian peoples, but that is another matter.

What Pynchon is referring to in this case is Soviet Union's introduction of Latin script in Soviet Central Asia in the period between 1926 and 1940 as part of a much broader Korenizatsiya (indiginization/nativization) strategy it implemented in its various non-Russian republics, which promoted indigenous cadres and creation of distinct national identities within ethnically-defined national autonomous regions. Alongside this strategy was a push to Latinize existing writing systems of most of Soviet Union's minority languages with Latin script, potentially expanding to major languages like Russian and Ukrainian.

In the case of Turkic Central Asian languages, which did not have a formed indigenous writing system and instead relied on adapted Arabic, this served to not only address mass illiteracy in the region, but also break with both the Tsarist-era policies, and the region's linguistic connection to broader Muslim Arabic-speaking world. At the time Cyrilic was not seen as an acceptable replacement precisely because of the Tsarist/imperialist connotations that it carried.

The campaign to Latinize Turkic languages was largely spearheaded by Samed Agamali-Ogly, a prominent Azerbaijani Bolshevik who lobbied heavily in favour of replacing Arabic scripts with Azerbaijani-developed Latin alphabet in early 1920s. His efforts eventually resulted in the holding of the Turkological Congress in Baku in 1926, which would be followed by the creation of an All-Union Committee of the New Turkic Alphabet where Agamali-Ogly was given chairmanship to oversee the implementation of Latinization policies. This Latinization push was touted as "the great revolution in the east" that would not only "free" the indigenous peoples from religious superstition and increase literacy, but also make them less dependent on Arabic-literate Muslim clergy, which was presented as a way to overcome "cultural backwardness". One also should remember that, while Arabic was the de-facto writing system of most of the Central Asian languages, literacy rates were incredibly low and, apart from a cohort of Bolshevik-friendly intelligentsia (many of whom were advocating for getting rid of Arabic), only members of the clergy would be able to read and write in it at the time.

As such, Latin was chosen, it being mostly free of old colonial connections, and a massive linguistic reform campaign was undertaken that created Latin-based scripts for almost 3/4th of all the languages spoken within the Soviet Union, expanding beyond its initial Turkic focus and including, for example, plans to fully Latinize Korean and Chinese languages (this had an added benefit of effectively limiting the cultural exchange between Soviet Korean and Soviet Chinese populations, numbering in hundreds of thousands in the Soviet Far East, with those within China and Korea proper).

In Turkic languages' case they were all based on the so-called Jaꞑalif script (literally "new alphabet" in Tatar), which the Soviet press referred to in Russian as the "New Turkic Alphabet" developed by Soviet linguists in early 1920s. Among Turkic languages Azerbaijani was predictably among the first ones to be Latinized in 1922, with Kazakh and Kyrgyz following suit with the majority of other minority languages in 1928. That said, much of the groundwork was already done and the period between 1926 and 1928 was mostly spent on adaptation of the Jaꞑalif script to local dialects and languages.

By 1930s there was a major ideological shift, with a move away from Korenizatsiya and national autonomy, and towards overt Russification and Moscow-based centralization. Opponents of Latinization efforts, who often argued that its proponents were anti-Russian and were fermenting ethno-national discord, would see most of Latinization efforts rolled back and replaced by Cyrillic script which in most cases would last until the fall of Soviet Union in 1991. In the cases of present-day Kazakhstan and Kyrgyzstan Cyrillic was formally introduced as the only official alphabet in 1940 and remains the official writing system used in both Kazakh and Kyrgyz languages today (even though Kazakhstan is planning to replace it with another, different version of Latin script within the next two decades or so), while many other Turkic speaking countries like Azerbaijan and Uzbekistan reverted back to Latin almost immediately after securing their independence in the 90s.

In other words, while Pynchon is broadly correct by noting the efforts to implement a new Latin-script based alphabet in Central Asia in the 1920s, it would more likely be undertaken under the direction of local Bolshevik-friendly intelligentsia, not Russian intelligence officers. Furthermore, much of the work was the actual proliferation of the new alphabets through training and translation, not their development. Lastly, while Pynchon talks about Tchitcherine doing this work while stationed in a remote "bear's corner", the actual development of the respective alphabets was far more likely to be done either from Baku or Moscow, or local urban centres (Alma-Ata and Pishpek/Bishkek in Semirechye in particular). It is not impossible, but someone like Tchitcherine, stationed in a place like the one briefly described by Pynchon, would more likely be working on either training local cadres, or conducting translations/transliterations of existing materials, with the bulk of the development work done by Turkologists and linguists.

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