The post where they describe what they're doing sure makes it look like that. From what was described, this is a massive refactoring and recalculation effort to pay down years of accumulated technical debt. Occam's Razor is probably good enough: they had tons of complicated rules in the system that goobered up their calculations, and they needed to get the large amount of ineffectual cruft out at some point.

There's even a clear note that the /top stuff should go back to normal after the recalc is finished and it's back up to speed.

Frankly, I was a bit shocked by the scope of it. Seems like a huge and terrifying update.