Well I have no idea whether this would be unusual or not, but if you generated a bunch of small transaction chains, and then did a single RBF to batch them into one transaction, then you might exactly get this behavior where you are eliminating a bunch of existing clusters in favor of a single new one.
In practice, I think the fees grow so large when conflicting with lots of transactions that this is probably not something that comes up very often, but people have brought up esoteric rbf pinning vectors in the past, so I just want to not preclude something from happening unless we have a specific CPU concern we’re dealing with.