In your post above, you falsely claim that the students are being accused of plagiarism. They are not. While plagiarism can be a kind of academic dishonesty, it is not the particular kind of academic dishonesty at issue here. Then, to complete your false equivalence, you try to re-frame the de rigueur practice of drawing test items from an item bank as plagiarism, which is just laughable and ignores both the purpose of the test instrument and the different roles of student and teacher.
I contest that the professor is too.
The word "contest" in the above context means "to oppose as mistaken or wrong". So your sentence literally reads that you dispute that the teacher is also cheating. Clearly you have been arguing the opposite.
I think it might be time to give it a rest.
Exactly 1/2 of a professor's job is constructing exams? What part goes to lecturing and preparation? Office hours? Grading those exams and class projects?
"Cheating in this definition is using someone else's work to benefit yourself..."
No, cheating is gaining an unfair advantage in some kind of competition by violating the clearly specified rules. Your definition certainly is not how the word cheat is commonly used, and I have no idea where you came up with it.
I think you are thinking of "plagiarism," which sometimes intersects with cheating, sometimes not.