I'm inclined to believe his assertion is made in good faith, even if some here might disagree. He may have reasons for his perspective, even if they are flawed. I think it's more productive to approach his viewpoint with an open mind and a willingness to listen, rather than being overly combative—assuming he responds of course.
In general from a narrative perspective, up until the day of showdown, I think it's better for the US public to underestimate the PLA's capabilities than to overestimate. This is why I'm actually fine with a lot of EN misinfo on PLA we see around.
(On the other hand, the CN public should absolutely have 110% confidence in the PLA)
It's not difficult to understand why he believes the way he does. Tyler Rogoway is an American writing in English for an American audience. His sources are American, or at least English-speaking. His knowledge is drawn from those sources, filtered through their lens, and his conclusions are informed as such. He knows far more about American everything than he knows about Chinese anything.
He can't know what he doesn't know. As far as he is concerned, unknown unknowns don't exist (otherwise they would be known unknowns). This is true for everyone, of course, but it's especially obvious when you are a third party watching these sort of cross-language misconceptions as bilingual observer. The flaw is always the same—the limits of your own personal knowledge are not the limits of reality.