Is the sunk cost fallacy always a fallacy?

[Edric O]

Here's a thought for (d):

Check to see if they're being honest. You don't have to trust them to check to see if they're lying. Kinda the opposite.

[...]

tl;dr: Yes, based on the facts he has, his plan is still correct. But he's deliberately avoiding seeking out new facts after being given a hypothesis that competes with his own model of events.

And it's a very human reaction. But not one conducive to good outcomes.

I agree. He is obviously making a mistake.

But his mistake isn't the sunk cost fallacy. It's a different kind of mistake. The sunk cost fallacy would be if he knew a better course of action existed but chose not to pursue it because "I've invested too much in my current plan to give up on it now." As far as he knows, however, no better course of action exists.

Stubbornly refusing to consider that you might have the wrong facts isn't the sunk cost fallacy. It's... well I don't know if there's a specific name for it, but in any case it's a different error.

Hubris, perhaps?