I provided 2 crash reports to point out the issue, representing the same bug in different situations.

The first detailing that this is an exception relating to a similar crash like: MC-177225.

Whilst the other details that this is an issue with the new block tag, which seemingly applies to only the wither rose preventing entities from spawning upon it (being tag:#prevent_mob_spawning_inside used before it was bound).

I assumed that this could possibly be due to the fix of MC-173115, and could be a clone of MC-148974, but either way, it occurs when disabling the main datapack of the game (providing loot tables, advancements and recipes and other customizeable data, so this should be disabled when wished).