• There likely could be other benefits to them sharing such as:

      1. when there is more than they can use, particularly that the mushroom does not like in their environment
      2. producing more leaves is likely highly beneficial for the mushroom, for shade both living and fallen, nutrients and cover with fallen leaves.

      Similar for the tree, but also mushrooms are recycling minerals from dead material.

      I don’t know if there’d be “stingy” trees (aside from vastly different nutrient needs), I could see it more of miscommunication or having too much difference with language/biologic pathways. EDIT: Also I gotta imagine that giant trees don’t even bother counting it for mushrooms so long as they aren’t stressed. Sugar water is in the grid, take as much as you want.

      • Trees that rely on myco networks usually only get giant because of previous myco networking bonds, which funnel excess nutrients between not just the fungi but also other trees within the system. And depending on the involved species, this sometimes includes multiple plant species exchanging nutrients.