Yep. It's a vaguely interesting titbit for anyone who wants to delve into that level of detail.
Though ultimately can't see any way to learn more from it than we already get from the annoying progress bar, or utilise it in any practical way.
Yeh,, also as they change the amount of people they let through / balance the load.
I didn't take much notice at the time, mid sale, it wasn't something out of the ordinary. You'd expect the server to be calculathing things like to this for analytics and load balancing.