While I agree with most of this (and have upvoted) two points stand out:

Also, are you familiar with growth versus static models of intelligence

I don't think bringing this up helps your point very much. While there are individuals whose apparent extreme talent blooms fairly late (e.g. Steven Chu who didn't really start being that impressive until he was in college), the lack of change of IQ scores over time on average is very robust, dating back to Spearman's original research about a hundred years ago. This is also true for other metrics of intelligence. By and large, intelligence is pretty static.

University professors don't tell students they are too stupid to contribute to the problems they are trying to solve

This is true, but professors do sometimes tell students when a problem may just be out of their league. To use an extreme example, consider a grad student who walks into his adviser's office and says he wants to prove the Riemann Hypothesis. That said, your essential point is valid, because even in that case, a professor could still direct them to some easier related problem or helpful question related to some aspect of it. So your basic point is valid.