So you know I am a fan of Edmunds and I agree, the bolded is true and the biggest leak in his game. It relates directly to the amount of space he's required to cover in his zone drops while being aware of receivers underneath or coming across his vision...part of the defense by design in nickle is to utilize his length in the MOF to add the extra DB BUT...he's still getting caught with his eyes in the backfield and savvy QBs make him pay. Brady used to do it, Mahomes has been the one to take advantage of it recently. It's a very valid criticism.
However, in man coverage his responsibilities are typically the RB where Edmunds is very, very effective. I would guess that the poor passer rating in 2020 is due almost entirely to the zone looks where he was simply the closest defender to the receiver, because in man he is a very effective pass defender. If you watch when we are in a man look and the RB goes flat or wheel like here he basically wipes it out:
He does this consistently and at a high level. Being able to win 1v1 in pass coverage vs one of Brisset's reads there (you can see him look at the wheel route as the RB turns his head) allows them to bring a safety down into the box to cloud the crossers instead of leaving him high to help w the flat/wheel. That's one of the reasons we get the sack here.
Basically, Edmunds is a McDermott player through and through. He's cerebral and reliable to a fault: he's always in his Agap on run fits, always in his zone or man responsibilities in coverage. His athleticism is almost secondary to his reliability, strange as that may sound. Now is he perfect, clearly no. There is a lack of big play ability (some of which is due to his style which is admittedly conservative due to scheme, some would wrongly label it a lack of physicality), being too easily manipulated in zone as stated, and sometimes he will make a mistake or take a wrong angle but you'd be hard pressed to find an LB who doesn't. He is a great scheme fit MLB for this defense.