it happens decently often actually, somewhere in the double digits for me i would guess. but still not super common.
what you saw is definitely how the system works sometimes though. guys get a small injury, drop to say 95 health, but then heal up to 100% when practice rolls a minute later, and then you often won't get a message. i have definitely gotten messages on guys who were at 100% but i have also definitely not, but i'm honestly not sure if something changed (in 3.0 seble cut back some of the messages he felt were excess?) or if there's a good reason it happens one way or another...