Though from a game theory point of view, leaving them on for a couple of seconds is probably ideal to remind anyone who forgets to dim their own headlights.
That said, I'm still not convinced your truck isn't doing the right thing. Even a mile a way you've got perhaps 30 seconds before you are passing each other. Is there much to be gained by leaving them on for a few more seconds? Seeing another car heading towards me is a much clearer and less likely to be forgotten trigger than "ok, about now my lights are probably getting annoying".
The feature seems to be poorly implemented by all manufacturers. I see Teslas driving around flashing high beams every night because they trigger on/off really quickly and the drivers seem oblivious to the rapid change.
On a purely practical note from someone who is very light-sensitive, a combination of partially closing the eye closest to the light and fixing your gaze on the the outer edge of your lane (such as lane marker or eode of road) almost eliminates this problem, even for modern stupid-bright headlights.
Added benefit of letting you see more of your own lane in spite of the oncoming lights.
I have a 2021 Tacoma, and its automatic high-beam adjustment is terrible. It does a reasonable job of turning high beams off when a car approaches, but it has a number of problems that make it unusable. After the car passes it waits too long to reactivate the high beams. That's when they're needed most; my eyes have already adjusted to the other car's headlights, now the road is dark again, and I'm still on low beams.
It's way too sensitive. When a car approaches from a long ways away, it sometimes turns high beams off for minutes at a time. It turns them off when there are widely-spaced streetlights on long empty rural highways.
I finally took the time to figure out where the switch is to turn off automatic high-beam adjustment. I do a much better job knowing when to dim and reactive the lights than the vehicle does.