If they see something that is specifically contradicted by theory of x, they should assume there's some wrinkle or some theory of y. They should not say theory of x explains something that flies in the face of theory of x. It means they don't understand theory of x.
You still haven't given a reason for why their formation of guesses should be constrained to only those guesses that presuppose that they understand well "theory of x".
For instance, if their previous lesson on heat conduction included a statement about how different materials conduct differently (meaning but not specifying the differences in thermal conductivities or the dominant type of heat transfer), then that "different" might easily be thought to extend to something that behaves like a Peltier cooler.
If you went to a building regularly and when there, once a week at least, your current understanding of topics was shown to be quite incomplete, at best, then how long is it really rational to continue constraining your guesses about "how" to only just those allowed by your current understanding of all the terms. Eventually it becomes reasonable to start considering that no term is so sacrosanct that you can't revise or extend it in the face of the teacher showing you some clever corner of the great mass of human ingenuity that we have built up over a few millennia for, among other thing, impressing our children.
See, they may have simply built up a reservoir of something like intellectual humility in the face of their own possible ignorance. Something, that if you can't see at least the possibility of, I have to think you may have all but lost entirely.
I neither said nor implied any such thing. No such meaning could be reasonably derived from my statements. I don't appreciate strawman arguments, or suggestions that I have "lost entirely" my "intellectual humility" even though my first post stated "I don't know" is not a stupid answer.