Looking back. I think the elders all kept asking him if he really didn't know about any of this, precisely because they couldn't quite believe that he could have come this far without his master explaining anything about Ki Deviation. So they'd keep asking him if he's really unaware, then talk around the topic in different ways in case his master had taught him but he just didn't realize or something.
It'd be like discovering a student solving advanced Calculus problems by painstaking drawing a bunch of bar graphs to find the limit (or something like that). And discovering their teacher had forgotten to teach them the actual equation, or that you need to add c when integrating or something.
Elder: Wait, did your professor never teach you Calculus? not even dx by dy? How about change over time? But surely you know that, when put in to this kind of situation, you'd have to put a +c at the end there?!
Student: Why do you old people keep talking in riddles?!
Elder: Bah, fine. Here's Calculus 101