You're correct in assuming that nothing is stuck in a queue.
Compared with other Fediverse platforms, a feature that Lemmy lacks is paginated outboxes. These would allow communities to list all the posts, because other instances could get them a page at a time (e.g. 20 for page 1, then the next 20 for page 2, and so on). Instead, they provide a non-paginated outbox with only the most recent 50 posts. An outbox for comments isn't really feasible without pagination, which is probably why they don't provide one at all. For votes, it's even less practical, and irrespective of that, it would go against the familiar hang-up about votes being private.
So if you're the first person to join a remote community, then 50 recent posts are brought in, but no older posts, no comments, and no votes. There's no way to get the old votes. If your instance receives some activity that makes it realise that it's missing something, then it will resolve it (e.g. it will often fetch an old post if it receives a reply to it, and fetch a comment if it receives a vote for it), but it will start that post or comment at score 0.
If you really wanted to be fully in-sync for comments, then you could script it to use the APIs for the remote and local instance. For the remote instance it would be something like: list the posts oldest to newest (limited by the amount you're missing); get the ap_id for each one, then login to your instance and ask it to resolve it. Then do the same for the comments in each post. Everything it resolves would be a score 0 though, and it assumes that the author hasn't deleted themselves in the meantime, or that their instance hasn't disappeared. Given that, I don't really see the point, other than trying to a completist about stuff.