The problem is that you're rationalizing that certain types of end-bosses will not fall to logic or talking to, and then you carry that argument toward games like Fallout, Planescape, etc. where actually, those particular bosses (The Master in Fallout, The Transcendent One in Planescape, or Nomad in Star Trek) are specifically susceptible to certain types of logic due to the peculiarities of their characters.
They're not the types of bosses you're describing.
The game-makers for Fallout and Planescape understand that some gamers want to have big boss-battle rather than wade through dialogue trees (which are dependent on the gamer following a particular strategy which makes those dialogue trees available in the first place - a power-gamer who likes to wade in and melee/destroy everything in their path is quite likely never to see those dialogue options anyway).
So rather than having the usual simple choice available in your typical FPS - big boss-battle, you ended up with choices - in Planescape you could battle the big boss by yourself, with a single party member or more party members (depending on choices), kill yourself which also destroys the end-boss, or use varying degrees of logic.
The Master's unique goals and characteristics were akin to Nomad's in the old Star Trek episode, and very susceptible to certain forms of logic.
You've basically been going down two paths with your arguments:
1) That you don't apparently like the concept of a boss who can be brought down with logic. In that case, if you ever play Fallout or Planescape, you can play it the way you want. The developers were kind enough to give a range of choices for a range of players.
2) That certain types of bosses aren't vulnerable to logic. That's correct, but those are the bosses in your typical FPS, in the IWD games, Diablo, Dungeon Siege, etc. For whatever reason, the developers of Fallout and Planescape chose to make these particular bosses have a weakness because their entire entity was built around a faulty form of logic.
I understand you're arguing realism and pyschology, but realism doesn't necessarily translate to games or other forms of entertainment, and psychology is not always terribly predictive due to the changes the human mind undergoes throughout time and the events a person is exposed to.
The Achilles heel or critical hubris that a particular villain has is deeply embedded in human entertainment throughout recorded time, along with the way that they were defeated through the discovery of that flaw.
Take Max Payne 2 - you can't kill Vladimir Lem at the end, no matter how many rounds you pump into his body (a tad unrealistic, but so are many rocket launcher battles). Instead, you have to knock out pins holdings his platform up to drop him to his death (similar requirement for ending Max Payne 1).
Developers have done myriad forms of defeating end-bosses by requiring the player to do more than shoot-dodge and pump tons of rounds into their adversary - destroy X-gadget and end-boss becomes weakened. Um, whatever, but it's a common convention used.
I don't see much difference with the end-boss having a critical flaw in logic, particularly if the end-boss' entire existence is based upon the flawed logic. And again, the developers in the cases of Fallout and Planescape were kind enough to allow different types of gamers to defeat the end-boss in different ways.