Lily of the valley doesn't seem to regenerate in flower forests with bone meal. Even when keeping in mind that flower gradients have changed since they also change in relation to Y level, this still doesn't seem to be intended behavior. All other flowers in flower forest regenerate fine in the same spot. **

Steps to reproduce:

Load up a 1.18 pre-release world and locate an flower forest.
Now find a patch of lily of the valley and destroy it, and then keep bonemealing the same block. You will see that you get an different flower instead of the lily of the valley. 

It didn't seem to be possible to regenerate lily of the valley anymore at all using bone meal, after spending quite some time testing different locations. 

Observed Results:
A different flower generates by bonemealing the block, while it still has the same XYZ values as when it first generated.

Expected Results:
Just like all other flowers in the flower forest, you should expect to repeatedly get the same flower when bonemealing a block with the same XYZ value over and over again.