Well, frankly, yeah. It's way, way, way outside the bounds of normal that something about it doesn't quite sniff right.
There could be several different reasons for it but most often the reason is that it's not 20 years of continuous training, and I have no doubt that your experience is any different. While it could be that he's declined to test for 15 straight years (going on the rule of thumb of 3-5 years training to shodan), it much more common, and therefore more likely, that, while he started 20 years ago, he has had long periods of not attending a school.
And that would be consistent with what he technically wrote but not consistent with what he was implying.
Peace favor your sword,
Kirk