Similar situation here with a patch of trees.

From the About: "The shadows displayed by default are estimates gathered through indirect means like crowd sourcing and low resolution data."

Not sure what low resolution data they are using for the trees (I can't imagine mine were crowdsourced given I'm the only house around). Probably not worth it for me but apparently the premium version has more accurate/current data.

It's coming from public LIDAR data, which captures both trees and the ground below them (and is able to tell which is which).

Can you point to which LIDAR dataset? I did not see any openstreetmap datasets with the tree present.

It says it is using openstreetmap, so you can probably edit that tree if its added to OSM.

After reading this I went through all the OSM datasets I could see (including double-checking the layers) and none of them showed the tree. Now I’m even more curious.