Summary:
According to changelog 23w31a "Chorus Flower no longer provides support for hanging or standing blocks". Chorus Flower can still support some hanging blocks (even though Chorus Flower breaks immediately):
Spore Blossom
Lanterns
Hanging Signs
Bell
Pale Hanging Moss
Also on Chorus Flower you can place:
Vines
Glow Lichen/Sculk Vein
Steps to reproduce:
Build a Chorus Plant pillar and place the Chorus Flower on the vertical side.
Place the above blocks on the Chorus Flower.
Observed results:
You can place some blocks on the Chorus Flower.
Expected results:
Blocks will not be placed.
Pale hanging moss is also affected by this issue. It can be easily photographed with /tick freeze.