Summary:
Chorus Flower cannot place any block that requires support (eg torches, redstone, bell, door...). Since this is a full block, it is expected to place any blocks on all sides (it will correspond to Java).

some blocks can be placed on the bottom side (after 1.20.0.20):

Block	Bedrock	Java
Amethyst Cluster
Buttons
Pointed Dripstone
Weeping Vines
Glow Lichen/ Sculck Vein
Levers
Bell
Hanging Signs
Hanging Roots
Lanterns
Spore Blossom

Steps to reproduce:

1. Place the Chorus Flower.
2. Try placing blocks that require support (torches, roots, pointed dripstone, weeping vines...) on it.

Observed results:
You cannot place any block that requires support on a Chorus Flower.

Expected results:
The block will be placed (for either side).