agree - the quality of the tester is very important. Some really don't know what they are doing. I tested 81.9 or so (being a sub 30:00 10K runner that made sense plus the PH D conducting the test was himself an athlete = very good cyclist).
Next test, a year later or so, in about the same shape a grad student tested me on same machine at a 54 or so VO2. Clearly he did not have a clue...for 1) he told me to sprint in the last 30 seconds (mainly because I was no where near maxed out) and not surprising to me is that I hit my highest VO2 during the cool down - just after the sprint. He couldn't understand that the test (at only 18 min) was not long enough and did not allow me to reach my max. Nor was he smart enough to realize at my running level a 54 would be highly abnormal.
Several months later, after more test on other athletes, this same guys tells me he had a woman (marathoner) who could maintain 97% of her aerobic max for an entire marathon. I advised him that to my understanding of these concepts - that was not very likely. It was more likely that her VO2 max (the way he tested) it was wrong. and if he used the same protocol with her as with me, I know exactly why.