I assume your objection is to the comment about his agility. Because a 300-lb guy with wrestler's build is carrying a lot less non-lean mass -- that shouldn't be controversial.
His position is not about overall athleticism. Nobody gives a rip about an offensive guard's 40 time, his broad jump, vertical jump, etc. What matters is a few specific athletic traits: enough agility to create an angle with the guy in front of him, and enough strength to push him away or at least not get bulldozed. Things world class Greco wrestlers do daily in practice.
Plus enough agility to occasionally pull or help out a teammate -- which also gets into film study and detailed knowledge of the playbook. Presumably an aerospace grad can figure out the mental part.
Coon will be better conditioned than the 340-lb guys, which means his agility and strength will degrade less over the course of a full game and a full season. (Also his decision-making will degrade less.)
Coon's HS recruit rating is immaterial today. He was a 250-lb LB prospect. Completely different skill requirement -- for example, interior linemen aren't expected to run sideline to sideline.
Presumably Coon will also be more disciplined than, say, the Titans' 2020 first round pick (also an offensive lineman) who's already out of football.
Completely agree that he's most likely to make the practice squad or not make the team.