[cooper12]

> they gave each language a different Cyrillic orthography than the rest to fragment them even further

That doesn't seem correct to me. Different languages require different orthographies because they have different phonetics. Compare the Latin script when used for English to German to Vietnamese to Turkish. Same thing with the Arabic script with Persian and Urdu. When tailored orthographies aren't used, the written representation becomes a poor representation of speech. Though even then it might not have been a perfect fit in the first place, requiring digraphs or diacritics. Or the spoken language can diverge.

[Mediterraneo10]

No, the Turkic languages of Russia often have very similar phonology, but the Stalin-era language planners intentionally chose different ways to orthographically represent identical features across the languages.

For example, Turkic languages typically feature front/back vowel harmony where stops are velar before front vowels and uvular before back vowels. This is represented differently in the Stalin-era Cyrillic orthographies for Karachay Balkar (к/къ), Kazakh (к/қ) and Tatar (just к with the following vowel letter showing the distinction). Bashkir neighbors both Tatar and Kazakh and is mutually intelligible with them, and it doesn’t differ at all in this feature, but its orthography was given к/ҡ just to make it different from the other two.