Hmm, that is probably an optifine issue as the Optifines are not finished for 1.17. When I had a problem with the animations it was because of a performance toggle. Try playing with those to see if it helps, hopefully, they will fix it in the next optifine version.
The Bedrock Floor will be extended to -y 64 in the Caves and Cliffs: Part 2 Update 1.18, that will be at the end of the year.
Yea I see this too