Accounts aren't migrated, but you don't need an account on lemm.ee to post there. That's the point of federation (note I'm not on Lemmy.world)
What happens when you try? Are you subscribed the lemm.ee sax community? If no one from lemmy.world has subscribed there yet then it may not be discoverable. Federation starts once a user subscribes. I just tried to crosspost it as a test but the lemm.ee community didn't appear. Probably because no one from my instance subscribed there yet.
Edit: just subscribed to [email protected] and sure enough I was the first from sh.itjust.works. Now that's its been discovered by my instance ~~I was able to crosspost your post.~~
Actually, spoke too soon. The post still hangs on submission. Maybe the federation process needs a min first? Odd.
I actually can't post there at all? Curious.
I'm at a loss, sorry