May 13th has arrived and, from what I can tell, there are no new episodes on Peacock - I don't have the service myself but a user on the wiki who does have it has pretty heavily suggested that there's nothing, judging by his response to me removing the mention of The Land Before Time from the article that started all of this (which was immediately reverted, re-removed by a fellow admin and was again reverted... it's not on there anymore as I write, but that might not stay that way for long).
I think it's safe to say that this was a false alarm - I'm not calling off the chances of something TLBT-related coming to the service post-official release, mind.