my "customers" were begging me to give them as little knowledge as possible.

More likely they were begging you to give them less knowledge than you thought made sense. Unless every teacher was getting the same response you were getting, perhaps your idea of the optimum amount was the problem and not the students idea of the optimum amount.

If the tests were fixed and completely out of my control, then as a teacher, I wouldn't be the bad guy anymore.

You would still be the bad guy if your idea of the amount of background understanding they needed to have to pass the tests was different from theirs. I tutored my daughter in 10th grade (US 16 year olds) chemistry and algebra this year. At a certain point while covering enthalpy of reaction calculations it was clear to me she didn't really understand charge and electrons and protons, she essentially had not sense of the Bohr atom. It quickly became apparent that 1) she did not agree with me that the best way for her to learn how to do enthalpy problems on the test was for me to take her backwards through the bohr atom and then back up the entire curriculum, and 2) she was right, my approach would have made sense if she was EVER going to use this stuff again, which it was clear she was not.

In New York State our high school classes did have state standardized tests. In my opinion, the dynamic in the classes was not particularly different in the ones with regents exams (standardized test) vs the ones that did not. However, it never struck me that in any of my classes that we particularly wanted the teacher to teach less I may have just been blind to that as I loved school and eventually became a professor, so possibly I was very atypical in high school.