I listen more closely when a former OL guy evaluates either a DL or a fellow OL.
Same thing for a LB/RB/WR/CB/QB, etc They played or competed directly against that POS, then try to listen more closely
Most of these evaluators watch a fair amount of film and I think it is more substantive when they hone in on the good and bad for a position they actually played or a position they directly played against.
Example would be any guy that played OL, then watched film of Aaron Donald. First words after watching were probably along the lines of, "!@#$ me to tears."
Doesn't mean their other opinions are worthless. Just less valuable via actual, accrued pain.