I've seen the graphs in that post, and it's pretty clear from how precisely kbin's graph tracks Lemmy's that what's going on here is some endpoint is being queried that counts federated Lemmy users as part of the kbin network. The numbers linked in the thread parent you replied to are the better ones.

I don't think anyone is trying to pull a fast one here. One of the big challenges of federation is keeping how different apps represent similar data in sync. I think kbin just has some user-count endpoint that quite reasonably counts federated Lemmy users as part of the kbin network (which they are). People are misinterpreting that data though as representing native kbin accounts, which is an incorrect interpretation (and probably incorrect presentation from the stats site... but almost certainly a well meaning error.