I have observed this behavior in 4.18.3, 4.19.2, and Main (CL 4048405)
I made a landscape, painted some foliage and saved the scene. After I saved the same scene under different name the connections between foliage and landscape is lost. The tree aren't affected by the height. This same is true for duplicating the whole scene, adding as a new level to other persisten level etc. Basicly, you can't do nothing beside that scene that you have started to paint foliage.
Result: Foliage position does not update to match new landscape height.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-58619 in the post.