I found the page about “phased upgrades” (somehow missed it searching for “staggered”, “incremental”, “delayed”, etc). Thanks for the pointer!
Unfortunately it doesn’t seem configurable on my end, and it rolls out in about 54 hours so it can take out most of my machines before I have time to react (my first machine might update ~20h into the phased rollout, the rest will break within 24h). Bummer!