Summary:
The bed cannot be placed in the air (when aiming, for example, at the vertical side of a block), and cannot be placed on non-solid blocks. This doesn't make any sense because beds don't need a support block. You can place a bed on solid blocks and then break the blocks and the bed will remain in the air.
The ability to place a bed in the air will also correspond to the Java edition.

Steps to reproduce:

1. Place the foliage.
2. Try to place a bed on it.
   ----> You cannot place the bed on the foliage.
3. Replace the foliage with a full, solid block (for example, a stone block).
4. Place the bed on it.
5. Replace the supporting block with a foliage block.

Observed results:
To place a bed, the player needs a solid block.

Expected results:
To place the bed, any block will be needed, since the beds do not need a supporting block.