Bells cannot be placed on top of cauldrons, composters, hoppers or other bells

The bug

These three blocks have a lip around them on their top face which is two pixels thick. A floor-state bell has two feet which are also two pixels thick and lie on this lip neatly without anything overhanging. Despite this, bells cannot actually be placed in this position (the three attached screenshots use /setblock).

Similarly, bells cannot be placed on top of other bells, despite the supports on top being the exact same as on the bottom of the block.