Slow rollouts can be quite quick. We used to do 3-day rollouts. Day one was a tiny fraction. Day two was about 20%. Day three was a full rollout.
It was ages ago, but from what I remember, the first day rollout did occasionally catch issues. It only affected a small number of users and the risk was within the tolerance window.
I don't know about this particular update, but when I used to work for an AV vendor we did like 4 "data" updates a day. It is/was about being quick a lot of the time, you can't stage those over 3 days. Program updates are different, drivers of this level were very different (Microsoft had to sign those, among many things).
Not thay it exuces anything, just that this probably wasn't treated as an update at all.
It was ages ago, but from what I remember, the first day rollout did occasionally catch issues. It only affected a small number of users and the risk was within the tolerance window.
We also tested locally before the first rollout.