Right, I get what you’re saying and if they aren’t federated to begin with then I don’t think there’s any issue. The issue comes when you federate, get everyone used to being able to interact with that user base and that content, and then defederate. The end result might be the same amount of users on lemmy in either case, but i’d wager the reception at that point is totally different.

In the first scenario, there is only slow and steady growth.

In the second, there is slow and steady growth, followed by huge, rapid growth, followed by a sudden decline that would make user interaction drop off a cliff, while the content and interaction is still available, just on another platform. I’d bet most people won’t be interested in continuing to use a “dead” platform.