Summary:
Clone MC-264563.
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
• Hanging Roots

Also on Chorus Flower you can place:

• Vines
• Twisting Vines
• Painting
• Item Frame
• Signs

Steps to reproduce:

1. Build a Chorus Plant pillar and place the Chorus Flower on the vertical side.
2. 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.