Sorry, it's me again. But that can't be right!
I've done some further test and for me it looks like that global setting "Passing Score" actually is handled as a percentage value.
See my test.
I've created a simple course having 1 quiz with 4 question scoring 1 Point each. So the quiz has a total of 4 points.
If "Passing Score" is set to 80:
Result for answering 3 out of 4 questions correctly is failed (red "75%" in the top right corner):
Now if I set "Passing Score" to be 70:
The result for the very same quiz is "passed" (see the 75% in the top right corner is green now):
And if you set "Passing Score" to more than 100 then you fail at the quiz (red colored "100%") even with all questions answered correctly.
So it's not just in my mind. The setting says "Passing score" (an absolute value, just as you explained in your second answer) but it actually is handled as a percentage value (That's how your first answer reads to me, despite the actual setting does not tell that it expects a percentage value.)
I think to get this straight at least the wording of the setting needs to be fixed.
And it should not be possible to set it to more than "100", because that will break quizzes.