Any source on this specific claim (ie. not Russian censorship writ large)? I get that Russia is unpopular right now, but is this just conjecture?
Also, generally information critical to the government, information on suicide, information on banned substances (this is the official reason why the Russian Wikipedia is banned), and information on making bombs and adjacent terror-related devices is also controlled, but I believe Z-library (and LibGen) don't host much of it.
The last thing I had paid attention to was the Russian government lifting the blocks on RuTracker, the most popular Russian-language torrent site, in reaction to the sanctions—to which RuTracker responded back by blocking Russia on their end [1].
But yeah, in that sense, it would seem that keeping people happy, having access to entertainment, scientific material, etc., and retaliation is more important than the ridiculous anti-LGBT laws right now. Maybe I'm wrong here, but I would think Russia does not pose a massive threat to Z-Lib and LibGen right now.
---
[1]: https://torrentfreak.com/rutracker-found-itself-unblocked-in...
Don't believe that is true for libgen, plenty of content critical of Russia, Putin, and also content that will teach you to make bombs on there.