Yeah, unfortunately that is a thing. Example:

https://lemmy.sdf.org/c/collapse@lemmy.ml (lemmy.sdf.org's local view of Collapse @ lemmy.ml) shows 22 subscribers. In effect, this is the number of people on lemmy.sdf.org who have subscribed to this remote community.

https://lemmy.ml/c/collapse (the original/direct view of Collapse @ lemmy.ml) shows 2.11k subscribers. I don't know whether this number shows only subscribers from lemmy.ml or an aggregate of all subscribers across the fediverse.

Unfortunately, another issue even if the count on the direct link to the community is an aggregate, is that it's probably not counting people who are stuck in a "subscribe pending" state. A ton of the communities I subscribed to weeks ago still show in this state on my communities page. I understand that what this means is that I'm subscribed on my end so that everything works for me, but the original community hasn't acknowledged my subscription, so I expect that this means it also doesn't count me as a subscriber.