Ah - well here we have it. You want one forms performance to be evidence that someone can fight, and another that they can't. I say neither prove this. Having "knowledge" of applications is not the same thing as actually being able to use it.
However, I would be bug-swallowing astonished if the nan quan guy hadn't had fairly extensive san da training as well, as that is a pretty standard wushu curriculum. I would also be astonished if, in most circumstances, the young monk didn't revert to san da for self defence.