Hello, there is a confusion with your changes, which is why I plan to revert your changes.
https://www.openstreetmap.org/changeset/166954694
https://www.openstreetmap.org/changeset/166954787
https://www.openstreetmap.org/changeset/166959742
The fact is that there are 2 similar types of borders in Crimea: "Russian" and "Ukrainian", for example:
Kerch: https://www.openstreetmap.org/relation/3826851 / https://www.openstreetmap.org/relation/2865044
According to Russian borders, there is a difference between the more "important" territories admin_level=6 (municipal districts, municipal districts other than St. Petersburg, urban districts, BUT also urban districts with urban divisions) and less important admin_level=8 (urban and rural settlements within municipal districts, inner-city municipalities, districts urban districts with inner-city division). This division is logical for a more convenient classification of territories.
https://wiki.openstreetmap.org/wiki/RU:Tag:boundary%3Dadministrative
This was confirmed at the forum in 2009.
https://community.openstreetmap.org/t/topic/46944
You can assume that these are regional features (some territories are marked with a more important tag). There is no such dependence for the Ukrainian administrative division, but there is a consensus in the Russian community and a different classification is used.