I didn't start a new thread on this - my post in the other thread (where I saw nothing indicating Dugger's mindset at the time) was moved by mods to its own thread.
I know how it works. The players you mention were not transition tagged. They were told to go out and see and come back with the offer. Once that tag is in place, negotiating becomes much harder, because you're asking a team to tie up millions in cap for a player they might not even sign, weakening them in the FA period for several days.
Also, these negotiations often take a lot of time and energy and in that frenetic period, I doubt people want to spin their wheels in mud.
I'm guessing that most of the safeties on the market weren't happy that S became the position of dump this year.
Given that, if the Pats hadn't tagged Dugger, they probably could have more easily come to terms with him if they really want to keep him, as he wouldn't have gotten any offers beyond their capabilities, right? And he wouldn't have any reason to aim his dissatisfaction at them.