Trees generate on top of each other in world gen datapacks

The Bug

Trees spawn on top of each other upon world generation, causing lots of tree skyscrapers. Relates to MC-237500.

To Reproduce

1. use the datapack listed on this report, it will give an invalid verification

2. press go back

3. press done, it skips the verification

4. leave the seed blank and create world

5. press safe mode, and proceed

6. look around

The Error

Trees generate on top of each other