Not sure thats completely true. I think those drafted high for their athletic abilities generally hold enough value to a certain hooded hc with a new boat. How many vet 1st rounders did BB bring in last year (on the cheap and for cheap compensation). Van noy, the guard in the jones trade, Mcclellin. I'm sure i missed a few. While the guard didn't pan out, Mcclellin and van noy contributed, albeit with limited roles (how many on here were saying "Collins who?" after Van Noy jumped the line to block the fg, iirc, shortly after Collins was traded).
I'd argue that draft slot contributes to interest from the 31 teams who have not had the borderline player on their roster, when said player is cut/trade bait/UFA. The athletically gifted raises an eyebrow, the less gifted probably isnt given the same regard. Often, the difference would be original draft position.
There was a good discussion here earlier this week regarding "athletes" and "football players." While it was vaguely agreed the football player generally has a more productive career, it was in regard to top flight producers. Id argue that fringe players (STs, limited roles, backups) generally will be more appreciated for their athletic ability, where the intangibles in this group tend to be limited, at best. The discussion in said thread was generally around WR, and did not denote a seperation of slot/split while relying heavily on 40/3 cone times.
Long story short, I disagree. While draft slot itself may not hold water, the attributes that land a player in said slot matters to a team contemplating giving them a shot to make the roster.