OP can you clarify something?
When you tap, does he stop immediately? Or does he still push the submission to the point where he thinks that should be the limit then stops on his own.
If it's the former, he's being kind of douchey, but whatever. If it's the latter, that's fucking crazy and you should tell your instructor. It's super abnormal and just plain wrong to continue a submission after a tap.
Even the guys in here complaining about when people tap to early, (sound like) they still let go after they receive the tap.
Out of all the perspective shared one thing I didn't see anyone say. Is that , if someone has a submission locked, and you do not know the escape, or it's too late to work the escape there is absolutely zero benefit in not tapping. By the time you feel pain, damage has already been done to your tendants and joints. Generally more than you think. For me , when i'm warm I'll think 'oh i'll be a little sore tomorrow I guess'. Then three hours after cooling down I realize I'm hurting a lot more than expected.
If someone has a kimura on you, you are not getting stronger/ more flexible , by letting them push the kimura to your limit.
Strength and flexibility are important, but you work on those with stretches and exercises not by letting people damage your body.
P.S to other posters
Sometimes people may be tapping early because they already have an injury. Like if my elbow is hurting from an armbar that went too far a few days prior, you better believe I'm going to tap if I don't escape immediately