I have a homelab with 24 disks (2x 12-drive raidz3 pools). In the past 15 years of operation I have replaced many drives. Usually my experience matches yours, but there is one time I got a simultaneous 3-disk failure. One disk failed, then when I replaced it and did a scrub, two more from the same pool failed in quick succession. I had to scramble to get more spare drives, and didn't sleep much while I waited for the pools to finish the scrub.

Coordinated failure is a thing, unfortunately. Drives bought together tend to fail together.