At stake in answering this question is how fascism, when it has emerged, changed the state in which it appeared. Unlike "classic" reactionary politics, which might impose the previous form of government on the population -- a republic overthrown in favor of a restored monarchy, e.g. -- revolutionary politics seeks the eradication of the previous locus of political power with something new. This might seem like a small distinction but it really isn't. It is a key reason among some important others (anti-leftism, ultranationalism) why the Nazis are rightly called fascists rather than mere reactionaries, despite their embrace of certain ideological positions that we might consider reactionary, like radical traditionalism.

We can better understand the distinction by looking at examples. The Nazis, as already noted, were revolutionaries in that they sought to replace the republic with a new dictatorial form of government, rather than restoring the Kaiser or another monarch. Although it was also antisemitic and highly authoritarian, the German National People's Party (DNVP) of Alfred Hugenburg was more properly understood as reactionary given its focus on restoration. Italy's case is perhaps more confusing because Mussolini did not abolish the monarchy in his country. Here, it's necessary to bear in mind that the practical form of government in Italy nevertheless changed: the parliament no longer passed laws and the king -- already limited in his powers constitutionally, become little more than a figurehead.

You make a good point about the importance of hierarchies and authoritarianism to fascism; the counterpoint here is that authoritarianism is not exclusive to fascism, nor even to the right generally. Further, embracing of hierarchies is a fundamental feature of right-wing politics generally, rather than fascism specifically. Here we can consider yet another example of a revolution that could also be judged reactionary according to the criteria you use: the Islamic revolution in Iran in 1979. It radically changed the form of government, abolishing the monarchy and replacing it with an Islamic republic. But it reinstituted civil limitations on women's rights, imposed rule by the mullahs, etc., all of which was extremely reactionary. However, we don't therefore fail to include the Iranian revolution among important world revolutions.

A final point to make is that there were plenty of reactionary regimes in interwar Europe that are commonly called fascist but that likely fall short to some extent of the mark. While Germany and Italy definitely had fascist regimes, the authoritarian right-wing regimes in Hungary, Romania, Spain, Portugal, Lithuania, Poland, and Austria (among others) during the same period were not fascist. Rather, there were fascist parties that might or might not have wielded power during the period (Arrow Cross Party in Hungary, Iron Legion in Romania, Falange in Spain, Nazis in Austria).

I find that the very best book that describes this distinction is Stanley Payne's A History of Fascism, 1914-1945. In that book, Payne provides a kind of taxonomy of right wing politics in interwar Europe, distinguishing among the conservative right, radical right (what we are referring to here as reactionaries), and fascism.

To better understand the more general distinction between right authoritarianism and fascism, my go-to texts are Roger Griffin's The Nature of Fascism and Robert Paxton's Anatomy of Fascism. Finally, Ernst Nolte's Three Faces of Fascism does a nice job of taking the notion of the "fascist minimum" (i.e., What are the minimum requirements for a party to be fascist?) and applying it in specific cases.