Its a very interesting question.
One arborist I know says taking all the dead out of a hemlock struggling with adelgid will really benefit the tree and it will come back strongly in conjunction with spraying. With that in mind, I have thoroughly dead wooded the big hemlock in my back yard. This tree has taken some storm damage over the years despite being well trimmed and cared for, always due to heavy wet snows. As I take deadwood out of it, I'm thinking now there will be less for the snow to stick to and less dead to block light to the live limbs (both being small incremental improvements) and less deadwood material for a squirrel to make a nest next season ( I wasn't happy about the damage done nest building this season as a good amount of live growth was ripped off for nest material).
In the classic Pironne text on trees, I believe he advocated leaving a dead limb on top of a tree for the sake of a bird perch.
Isn't conventional thinking that removing deadwood removes an entity that can foster insects or disease that could harm living parts of the tree?
Google provided this thoughtful and deep article by a climbing arborist (in the Detroit area, maybe
@kevin bingham knows him)
Does removing dead wood actually help trees? — Tree First - https://www.treefirst.org/removing-deadwood