Summary:
Almost any blocks can be placed on a decorated pot. This results in a z-fight, and floating blocks that require a supporting block. In Java, you can only place certain blocks on a decorated pot:

I'm not sure about the block placement on the top and bottom of the decorated pot, but on vertical sides should not be placeds blocks (as they will float).

Steps to reproduce:

1. Place the decorated pot.
2. Place blocks such as buttons, torches, levers... on the vertical sides, and on the top redstone, redstone repeater / comparator, doors, glow lichen, sculk vien...

Observed results:
Almost any blocks are placed on a decorated pot.

Expected results:
Blocks that do not fit (larger than sides) on the sides of a decorated pot should not be placed on it.

Screenshots: