I think bluesky is fetching posts before displaying anything, whereas graysky shows skeletons as soon as it has the list. This has the advantage of only fetching posts that are visible due to the fact that the list is virtualised (although it makes the page a bit jumpy)
Oh and I suppose that since posts are cached individually, you don’t have to refetch every post every time. In that case where you have one new notification in a list of 50, bsky will make 51 requests whereas gsky will make… 2
