Ask HN: What does gmail do when showing the “Loading” screen?

I'm curious if anybody has investigated this. It seems like (a) it should be unnecessary to have a loading screen at all for a mostly static page, (b) even for a lazy-loaded dynamic page there shouldn't be all that much involved in loading your last 100 emails, and (c) it's the antithesis of google to make things unnecessarily slow (okay debatable, but most of the time speed seems like a primary concern for google).