Don't really know what this is from but now that I think about it I think this is going to be pretty intercooler system dependent, because of the capacity/effeciency of how much heat it can remove. IOW, a wider ranger of input temps(cold air intake vs. not) may result in relatively narrow output temps as he measured, BUT that's because of how good his IC is. A smaller capacity/efficiency IC system would result in a wider range of output temps as a function of input temps. Or put yet another way, his measured ratios would not map to other setups independent of the specifics of the IC system.
Practically, I would suggest this means that if one has a very large/effecient IC setup, then cold intake is probably irrelevant, and vice versa.
But maybe in the real world, all intercooler systems are sufficient to make cold air intake irrelevant.
