The bug
When a 2x2 spruce tree grows, dirt variant blocks (grass blocks, ...), foliage blocks (grass, flowers, etc.) lower than the blocks the saplings have been placed on prevent the blocks below them from converting to podzol.
Linked issues
relates to 2
Attachments
Comments 18
Can confirm that this was an issue in 21w11a, however, I can no longer reproduce this in 21w13a, meaning that this problem was fixed in this version.
Can confirm in 20w46a.