I was about to make a report about this too.
Tested in a Soul Sand Valley fortress:
Creating a large Nether Brick spawning platform on a crossroad in the fortress resulted in no spawns after ~1 minute in 20w21a but downgrading the world to 20w20b fixed the issue
David McGurk
I was about to make a report about this too.
Tested in a Soul Sand Valley fortress:
Creating a large Nether Brick spawning platform on a crossroad in the fortress resulted in no spawns after ~1 minute in 20w21a but downgrading the world to 20w20b fixed the issue