Even that is subjective speculation and not objective fact. Lot's of Heisman trophy winners and projected 1st round picks have been out performed at the NFL level by non-Heisman winners and 3rd round or later picks.
Would you say that Kamara was not as talented as the RB's drafted in the first and second round the year Kamara was drafted?
It's all subjective speculation which is why it's so weird to me that so many people seem so confident they know how successful or not any college player will be in the NFL. Nothing about the future can ever be known. We can only ever speculate and guess about the future. Even when the future turns out as we speculated and guessed, we still just speculated and guessed.