I wish there was some kind of way to show these folks the feeling of vertigo, when instruments no longer make sense or suspected faulty, that would be great. But there is no such simulator on the ground, which could trick your inner ear that way. (Maybe there should be.)
I took a long pre buy test flight from NJ to Alabama in the place I was going to buy, a TB-20. I had my PPL and maybe 100 hours. The seller , a CFII, was with me. On the flight home we had an IFR clearance and I was flying. Climbing out we entered some cloud. Within a few seconds I was all twisted around. Bob took over , leveled us out and we soon VMC and on course.
I could not believe how quickly I was totally sideways. Until you have experienced it , it is hard to comprehend.
I brought the plane and the first thing I did was get my IFR. Really no point in flying without it. Just too easy to get caught.