I fail to see how it is untestable. It might be impractical to test, but if the survival of all humans suddenly depended on their future programming skills (e.g. because a dictatorial alien appears and decides to kill off any human they can't use in their programming slave workshops), it would certainly be tested, as far as I can tell.

I also didn't really define my usage of the word "effort" very clearly or unambiguously, which is intentional: I'm not in the best position to determine/figure out the exact line at which the scope of the term "effort" should be drawn for the statement to be solid.

The alternative, however, being that a person simply cannot learn and obtain talents, would imply that some individuals have a meta-talent for obtaining talents, as it's been demonstrated before that people can (and often will in extreme situations or environments) adjust in such a manner. This, to me, seems much more complex than "Everything can be learned, including talents and how to obtain talents", so by Occam's Razor I prefer to believe the former.