Hi, just like average accuracy, i think it would be cool for an average spin speed status for people, so you could actually know how fast someone like WWW spins without watching his replays/spectating. Sorry if this is against request rules.
Even assuming this was implemented, it's not actually stored on the server anywhere yet, so it would be limited to the average of new scores only. That would make for a pretty weird statistic.
i know it sounds dumb, but it doesn't really matter if it starts the count now, of what my friends told me, the pp system was implemented when a lot of people already played. so i think there really is no problem if it starts the count now.