> 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.