I checked the Updates page for this game on Steam from August 18, 2023, the date that the demo was announced as being released, to the present and there's nothing in any of those update notifications there that mentions anything about any voices (Russian or Japanese) being omitted from the final release, so I would say that the Russian male voice should still be in this final release version.
i suggest you to delete the russian voice folder inside the .zip so it will unpack faster, but you still have to wait for the other one to unpack cause the .ogg files are slow
I ended up buying the game, never played any horror games other than this and Hollow Cocoon, but damn this one is SO good! Meeting different "flawed" Mita feels like riding a emotional roller coaster.
By the way... interestingly... the "pause" or "cut" between each Japanese voice lines feels unusually short, I treat it like AI reading out paragraphs if you get what I mean.
https://www.youtube.com/watch?v=CR6Yml9smqI
Gameplay --> https://youtu.be/1Lw0gD6pd3w
https://www.youtube.com/watch?v=UVMJ2apsI94
By the way... interestingly... the "pause" or "cut" between each Japanese voice lines feels unusually short, I treat it like AI reading out paragraphs if you get what I mean.