“Fully cooked” food and reheating

I just ate some chicken tenders that are fully cooked from frozen but are supposed to be heated to 165 f. It says to microwave for 1:30 but I did 2:00, most were super hot but one wasn’t as hot and I fucked up and didn’t temp them. The “cook to 165” is more just a liability thing right? And it could’ve been 165 in the microwave?