You’re assuming it only consumes exactly what it needs to survive and not even a small amount more than that. You’ll have to prove that. Pretty sure they probably keep some buffer or give priority to their own species or certain species, making the network their own buffer. Would that be mushroom racism? I don’t want to learn anything from racist mushrooms man.
There’s a big difference between storing energy for the winter and being obese.
Mushrooms aren’t simply favoring their own species, they are favoring species that are cooperative. If they perceive a species as obese or cancerous, they will fight to control those surplus resources.