Cannot place sea pickles on soul sand

This could be due to Soul Sand not being a full block. (You slightly sink into it when on top of it, much like a stacked snow block.) You cannot place the Sea Pickles on honey blocks and path blocks either, which are also not full blocks. So I believe this is working as intended.

@Dawn Sunset
Soul Sand has been updated in 20w11a, allowing more blocks (doors, rails, buttons, pressure plates, redstone and more) to be placed on the block, so it would make sense that Sea Pickles would be included

^ precisely, linked ticket explains it all

Discovered while testing, not relates to

Confirmed in 1.16 Pre-release 8.

Removed nether foliage from title as it was added after the ticket was assigned and is already WAI: MC-191255