Trial spawners can spawn mobs in mid-air since 1.21.2

Previously, trial spawner will try to find a solid ground for mobs to spawn on top of. This behavior is last seen in version 1.21.1

With the release of version 1.21.2, this behavior changed. Now trial spawner freely spawns their mob in mid-air, just like how regular spawner works.

I have yet to find this change documented in the release notes.

To reproduce this issue, a simple superflat setup in 1.21.1 suffice (sample setup attached):

• Place a trial spawner at Y=0 set with zombie spawn egg (using `/setblock ~ 0 ~ trial_spawner` would do)

• Put a stone 6 blocks away from the spawner to stand on

• Change the gamemode into survival for 1 second to activate the trial spawner, and then

• Change back into creative.

• Do `/tick sprint 60s` to quickly observe and note the behavior.

Observation:

• In 1.21.1 with the test setup, the trial spawner will only spawn mobs on top of them.

• In 1.21.4 with the test setup, the trial spawner spawn mobs anywhere within its spherical distance, including mid-air.

Personal take:

This behavior change breaks 1.21.1 key farms, and may have caused those key farms to be redesigned – but reverting this post-1.21.2 behavior to pre-1.21.2 behavior may not really harm "fixed" key farms.