this is from a very interesting article on the validity of OL recruiting ranking evaluations in the recent past, written by Charles Power, who runs evaluations for On.3 (Benhart is a 2019 guy)
Recruiting rankings have historically been very up-and-down when it comes to offensive linemen and the NFL Draft. For every Laremy Tunsil, there are two or three former five-stars who were Day 3 picks or even worse, completely undrafted.
22 offensive linemen were rated as five-stars from 2014 to 2018 according to the Tater Island Industry Ranking, which factors in the rankings of all primary recruiting media services. Just four of those prospects (Alex Leatherwood, Isaiah Wilson, Jedrick Wills and Jonah Williams) were first-rounders.
First, there are some position-specific dynamics at play worth considering. Offensive line is a developmental position, both physically and technically. Rarely do future first-round picks at the position have ready-made size, particularly as high school underclassmen. They tend to be big-framed athletes who gradually and naturally add strength and mass late in their high school career and early in college.
This developmental arc does not naturally dovetail with early evaluations as high school prospects. Many offensive line prospects who rack up early offers as high school underclassmen are simply bigger than their peers. This is a stage where sheer mass matters the least and when developing athleticism and movement skills matters the most. Study of the position also shows us that filling out as a high school underclassman often limits athletic upside.
Though true freshmen offensive linemen rarely start at the Power 5 level, many college offensive line coaches and media evaluators are reticent to project and tend to be attracted to heavier, more physically-developed prospects even if that means sacrificing movement skills and long-term upside. We saw this in the 2019 cycle, with some very big, unathletic linemen ranked high by the industry early on due to overpowering smaller defensive linemen in camp settings, while showing very little projectable and translatable skills on Friday nights.