Tapping to "not quite there" sub?

Last night a guy was going for a keylock from inside my half guard.  He had the hold on the arm, but I still had room to move and defend so he couldn't quite finish it.  It hurt somewhat, but not to the point where I was worried about an injury or anything because he didn't have much leverage on it.  A few things went through my mind:

1)  Tap, because he does have the lock and it was painful, but then explaining to him that he didn't really have the leverage to finish it properly might come off as kind of asshole-ish.  "Well, I tapped this time but it didn't really hurt that bad", you know?  But by not tapping he might think he was doing something wrong and get discouraged, when the reality was that he just wasn't in an optimal position for the submission.  Plus I was having to defend like hell, because had he passed my half guard he would've had it easily.

2)  Don't tap, because he wasn't going to be able to finish from where he was at and I didn't want him to get used to getting the tap from that position.  This isn't some TMA class where we tap in advance and say "Man, if you just could've gotten to mount or side control that would've been a good one."

I don't know.  I don't want guys learning bad habits, nor do I want them getting discouraged and abandoning moves that will work for them, and I damn sure don't want anyone getting hurt.  So what do you guys think?  Thanks.

BTW, the reason I'm concerned with what they're learning is that I'm totally the instructor.  If this was just regular training I more than likely would have just tapped.

Don't tap. Coach him from the bottom and guide him into a solid position. When he gets it on correctly have him put pressure. When you feel it tap.

Sounds like a good idea.  Thanks.

Tell him that he will be able to tap some people from there. For the people that won`t tap use it as a distaction to pass to side control.

Tap, shake hands and say "good job", then roll again.

Rinse repeat.

Experience will be his best teacher. When he finds that he doesn't tap everybody with his keylock, he'll find a way to improve.

I wouldn't correct him, if he tapped you.

"What the fuck are you talking about?!"

which one is you and which one is your partner?

advise him on what to do to get it on fully (whilst still rolling)

what cprevost says makes sense

One of my instructors, does that. When I am going for something, and I am not really getting there, he would talked me into it, and then tap.

I benefited from that kind of rolling when I get the opportunity to go on the mat with him during training.

Edit: Two of my instructors do that.

It's total BS to tap and then try to explain away the tap. If you are in danger, tap. If not, fight through it and THEN explain what they could have done differently. If you have to tap simply because you're unconfortable, own up to you're lack of mental tuffness, slap him on the back and say good job.