related to MC-246909.

normally, if there's a liquid that's one block above the cactus, the cactus will break, which is intended due to the fix of MC-123051. however, it's only affects water, lava and bubble column. any other liquid block (seagrass, tall seagrass, kelp, kelp plant and waterlogged blocks) won't break cactus.

step to reproduce:

step 1: place a sand, then place a cactus on top of the sand, after that place water on top of the cactus -> the cactus breaks.
step 2: remove the water, then place a cactus on top of the sand, now place the any block that can be waterlogged (in this case it's iron bar) on top of the cactus, now waterlogged that block -> the cactus doesn't break.

note: the same thing happens to segrass, tall seagrass, kelp and kelp plant, but it's harder to reproduce. the way to reproduce is by MC-190526. however, that doesn't means that this bug is a dupe of MC-190526 or MC-31100.