What rank is your instructor? It sounds like he simply doesn't know enough to teach you when to tap, and hasn't instructed the younger folk at all.

I think we're missing something in a language gap....

Your instructor/coach may have told you that your ukemi is good - but he may not have said "for your present level of experience".

I was practicing a while ago - shortly after the nidan grading - and was complaining to the instructor (a 6th dan) that I wasn't getting some part of what he was teaching.. His reply was along the lines that I was getting better - my technique was fine for someone who was not yet a black belt but I was learning it well enough that I could tell when something was off...
And that's not really a good description of what he said.

Your ukemi and throwing may be good "for someone with 3 months training" but when you get to three years training you'll know that it probably wasn't "good"...

BTW I still struggle with the dozens of ways to do Kotegaeshi... oh.. and all the rest of them. After 17 years.