That's what I was going to say - that ravens don't have crests to be shaved off.
Perhaps that's why the raven *bird* itself - not necessarily *that* one - is considered the opposite of Minerva/Pallas Athena's white owl in *this* incidence.
The fluffed and feathered owl of wisdom, besides being white and therefore "pure" and "good" symbolically, would be the opposite of the poor old nearly bald black raven from Hades.
There is one story that Pallas and Athena had been siblings or friends and that Zeus had taken his scepter to them when they were fighting one day. Pallas was scared and looked away, so Athena decked him and then took his name as hers. That could be another layer of the fraidy-cat Pallas reference.
The person speaking has seen the raven fly in and presumptiously alight on Pallas Athena's head, so he knows the raven isn't craven or cowardly - it's bold and brash, crashing the narrator's pity party, uninvited.
So, I don't think Nevermore has been shaved or is a bald eagle pretending to be a raven. I think ravens in general are shorn and shaven in comparison to more full-feathered and crested birds.
He's a crow, but a little bit handsomer - tho not much.