The purpose of gap coverage is not to fill a gap by hopelessly engaging with an OL while the ball crosses your path and you don't disengage.
The film does not lie: Edmunds is tunnel vision focused on meeting an OL in a hole, at the cost of letting the ball carrier cross in front of him. He is also unable to disengage to attempt a tackle. This isn't some inflexible system, it's a screw up.
I will tip my hat that other players like Poyer, who gets buried. And Hyde could have stopped the TD, but Edmunds is mainly at fault.