[MC-146790] Mob spawners no longer spawn mobs in air blocks

This bug only came about in 19w13a, mob spawners worked properly in 19w12b.

In order to reproduce,

Find a spawner (blaze, zombie etc.)
Clear around the spawner so there are no blocks, at least 9x9 area.
→ You will see spawns only happen on the spawner, if there is no block blocking a spawn from occurring.

Linked issues

Can confirm

Can also confirm, my skelly farm is broken 😞

Same issue here, most of my mob grinders are currently useless :/

Same issue, confirmed mobs only spawn on blocks at spawner level within the 3.5 block distance. They are no longer able to spawn in the air

Serious issue. Can confirm Window Java 19w13a. All spawner based farms are broken.

Same thing.

Confirmed for any naturally occurring spawner in any type of world on any vanilla java 19w13a snapshot version of minecraft.

Confirmed for zombie and skeleton farms.

Confirmed. Skeleton farm.