Pirates want to stay on Reddit? This is the last group I had expected to have such a reaction, but here we are. Yes, the mod could have worded it better, but these people actually want to stick around on Reddit.
I personally find Lemmy to be a perfectly viable alternative to Reddit for such subs. I wonder about the reasons why these people still don't want to move.
People's resistance to change is quite strong, even if they have good reason to leave and lemmy/fediverse are great alternatives the fact is that in terms of UX lemmy can be quite different and takes some time to find and rebuild a list of communities to join, specially since you can have the same community on different servers (i.e. technology on beehaw vs technology on lemmy.world) and just this fact means a learning curve for people that for the most part don't like change.
For example, the NewPipe community on lemmy.ml is tiny and pretty much dead, whereas the Reddit one was much more active. Communities like that which have reopened might make people want to stay on Reddit, unfortunately.