I think the only way for now to make trees "lethal" is to make one big invisible box around a set of trees, much like the old Il2 trees where the ones made out of 4 planes with 4 different textures on them were collideable but not the ones who were "actual trees"
It's never been a problem for me, but I guess on line it coud be a trick to get away or to sneak up on targets , but since the landscape isn't completely planar that won't work in the long run
