I find it strange, since lore-wise the tree beacon harvests bits and pieces when the tree grows, but the tree is gone and all thats left is a few blocks of leaves seperated in mid air.

Perhaps isolated leaves should be removed faster (i.e something like leaf decay.)

Due to the fact that this aims to be compatible with anything that is basically firing a event describing that a tree is growing - which is just a collection of blocks - i can't define what's a leaf and what's not on a reliable basis. For this to be implemented in a proper way, Forge might need to actually finally include a form of tree-registry where proper sapling, log and leaf blocks as well as a respective generator are defined. However, said thing has been denied in the past twice already for whatever reason, so as there is no proper way to determine if a block is a leaf or not, i can't implement a proper algorithm that would capture this on a reliable basis.