If players literally only ever remove resources from the walls of caves, and never the solid rock, then by nature of randomness, the cave walls will become less populated on average, because its going to reinsert more resourcres randomnly, and theres a non-zero chance that the replaced resource will not be on the wall.
On the other hand, if there is a cave which used to have resources on the walls, and now has none at all… it also means “behind the walls” is more dense than average with resources too for that chunk 