Seems like it would be more sense to just produce Katanas the whole time, especially since they're better designs than European sabers. Instead of putting a Katana blade onto a Saber's handguard.
The Guntō (軍刀) was a Japanese sword that saw use by the IJA and IJN during the Meiji period. The sword began seeing greater use following the implementation of military conscription in 1872. The Meiji period took place during the first half of the Empire of Japan, and began in 1868 and ended in 1912. The Empire of Japan lasted from 1868 to 1947. During the Meiji period, Japanese culture and society distanced itself from its former isolated feudal system and began to westernize. Inspired by many western ideals and standards, Japan introduced reforms such as the Five Charter Oath. They also made practicing Christianity legal. Overall, the Japanese allowed themselves to be more influenced by Western ideology, and began identifying with it.
As a result of this, the swords developed during the Meiji period, more specifically the kyū guntō (旧軍刀), had Western influences. These influences led to sword styles resembling American and European swords of the same period. The kyū guntō swords, used from 1875-1934, had things such as the D-guard (wraparound hand guard) and chrome plated scabbards. They could also include more luxurious additions such as silverworking and jade, and it wasn’t limited to just this.
In the early 1930’s, nationalism began to strongly increase both within the military and even the general population. This led to the introduction of the shin guntō (新軍刀) for the military in 1935 to satisfy the wanting of stronger identification and pride in Japan and it’s culture. Nearly all of these swords were produced by the Toyokawa Naval Arsenal from 1935 to 1945. These swords, in order to identify with traditional Japanese roots, were modeled after the slung tachi. The slung tachi saw use during the Kamakura Period from 1185 to 1332. Additionally, the Kaiguntō (海軍刀), the Type 94, Type 95, and Type 98 swords were produced between 1934-1945. All of these swords shared the same idea as the shin guntō, to relate back to traditional Japanese swords.
TL;DR- From 1868-1912 Japan began to westernize and adopted western culture and ideas. This led to use of the kyū guntō which was styled after American and European swords. But as nationalism increased within Japan, the shin guntō was implemented. This is due to wanting to relate back to Japanese culture and to more satisfy nationalism.