Bells cannot be placed on the sides of upper slabs, stairs, the side of a piston base, or the stone side of floor bells

Shown is a screenshot of bells placed onto the top halves of slabs and stairs using setblock. There is clearly enough space for the bell to be placed on the specified area of the block, however manually placing a bell on them through the inventory will not work.

Other blocks with a large enough placeable area, such as cauldrons, hoppers, and certain anvil orientations cannot have bells manually placed on them.

This may be considered working as intended, however given the changes to supported block placement on transparent blocks in recent snapshots I'd rather report this just to be sure.