Ie. the base of the tree can hang out over the void, looking quite odd:
https://ibb.co/MCvH7B4

should be fixed in my fork (indev) : https://github.com/quentin452/enderoni-continuation/

It looks like the trees only follow a couple of specific shapes. They're pasted into the world block-for-block instead of more organically like vanilla trees which can have slightly different heights and branch locations.

Checking to see if a tree would have more than 25% of its base over the edge might be easier to implement code wise.

I doubt this mod will ever be active. Unless you're willing to continue this mod, then its dead.