In the 1.21.70.20 preview, it appears several more cross models have been fixed to be mirrored correctly. However, several of them now have Z-fighting between their old and new models. This includes:
Crimson and warped fungi
Nether sprouts
All potted plants except for mangrove propagules (still mirrored incorrectly), cactus, eyeblossoms, and bamboo
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Can confirm, although they only have z-fighting on some coordinates. For example, if their z-coordinate is at 80 then they will look normal, but place them almost anywhere else and they will start z-fighting.

I cannot reproduce this issue with any of the following blocks from your list when they are not in flower pots:
All flowers
Mushrooms
Saplings
Dead bush
Fern
Nether roots
Azalea and flowering azalea
Here is a corrected list of blocks which have z-fighting issues:
Crimson Fungus
Warped Fungus
Nether Sprouts
All potted plants

This issue still occurs with Crimson and Warped Fungus in 1.21.70.22.

Also still occurs with the branch part of azalea and flowering azalea potted flowers
[media]
Confirmed