I think the point being disputed is not the narrow running of Agressor vs defender, but rather the tendency of the bosses in question to be insanely confident in their own prowess and/or completely ignorant of the protagonists prowess.
The majority of combat presumably not being with a batch of dudes dueling over who is the Best Fisticuffs in the World, but rather theoretically in pursuit or defense of their goals and logic reasons taht have brought them into your conflict with your character.
I hear what you're saying and I agree - that's kind of what I was getting at with the writing could be better here to avoid pumping out samey belligerent d-bags over and over. What I was more getting at is the general concept that in real life most people only enter into fights because they think they're gonna win, or they're being forced (by internal or external circumstances). And that totally meshes with being in pursuit or defense of goals - its just that characterizing someone as a belligerent d-bag is much more likely to create a straightforward, easy hero/villain conflict.
Its lazy, and an overused trope, to define a villain as a person you want to beat up (and not feel bad about it) as a larger than life "death by hubris" character, but its done because its an easy shorthand to express how you're supposed to feel about a guy you're going to kill if you plan to beat the game. I get that, I just wish they would at least make the confidence interesting to watch. Senator Armstrong was a trip to watch chew on the furniture, and although fundamentally he was clearly entering into the conflict because he was sure he would win, he's still way more engaging than the bog standard "what chance do you have against me" types.
If you've played Hades at all you can see it pretty much laid bare. Avoiding spoilers, some of your midbosses are a person fighting for her employment, a mindless beast, and a douche. A person forced to fight, and two who just think they're gonna win. Hades is a great game, but they absolutely leaned in to some shortcuts on the majority of the midbosses so they could spend time characterizing everybody else instead.