This is a reported bug. Looks like they are testing some fixes, not sure when they will go live. https://github.com/LemmyNet/lemmy/issues/3588
In any event, those old deletes will never get federated out. You will need a local mod or admin to remove the items from lemm.ee
Lemmy still has some issues that need to be addressed for it to fully replace Reddit for my needs
Be honest, do you still use reddit?
There is no easy way to do this. Each Lemmy instance uses their own autoincrement ID for posts. So post 12345 here might be post 54321 on another instance.
It has been suggested that each post gets a universal ID (UUID is an example). Then the local server could just examine the URL and redirect the user to the local post. This suggestion hasn't gotten any traction. The dev team is more focused on fixing the huge performance issues right now.
But when you first subscribe, you’d expect to be missing old posts
OP didn't expect to be missing old posts, hence his question. I had the same surprising discovery. Not sure how the UX could be improved to convey to the user what is actually happening.
Unfortunately, as one of those 3.8k daily users, I'm still using Reddit mostly. Lemmy has a long way to go before I drop Reddit all the way.