The next time you see the lady, say, ‘Next time you have a thought…just let it go’.
LOL.
First of all, if that type of trot is what your young green horse can do without completely losing his balance and going bananas, that IS his lengthening, regardless of what anyone else thinks it ‘looks’ like.
He won’t actually do an extended trot until he has learned to collect and sit on his rear end and push. He isn’t doing that yet, not to that level (he will at 2nd third level).
He is doing that to the extent that he can now, in the shape he’s in with the balance he has…in other words, that IS his lengthening.
As far as just having the test turn out successfully, if you have a very talented able young horse, when you ride your test, you are a lot more concerned about the WHOLE test than the lengthening, you do what you can and should do, and not one whit more than what’s good for the whole test and the horse. In other words, sure, but don’t overdo. I wouldn’t repeat it over and over, even in training, and wouldn’t go max full out at the show, either.
You need to be able to do something that shows a difference between your working trot and your lengthening. The more of a difference you show, the better your score will be…UNLESS…unless that big difference means you have to leap on your horse’s head to try and get him to STOP doing that whatever-you-want-to-call-it different trot by pulling on his ears and screaming whoa before he leaps out of the ring on the other side.
I would also not get too greedy and ask for too much, I think it’s better to have your test look like happy-energetic-eager-obedient-horsey overall.
However much you can do, and still control your horse and steer him and continue the test without him feeling like he needs to spend the rest of the test popping wheelies, is ok.