It may be similar to the idea that if you are deemed to have imposter syndrome, then you cannot be an actual imposter, so if people perceive you to have imposter syndrome then it's in some ways a good thing.
It's impossible to know if the author has imposter syndrome or not without some way of measuring his competence. However, I think "imposter" has become a loaded term as a result of the syndrome it's associated with. There are cases describing workplace incompetence, or not being qualified for a job, or being rejected for cheating at interviews, but there is no discussion of imposters in those cases. They're just deemed incompetent or not the right fit and moved on from. Actual imposters who game interviews and do manage to land jobs aren't called imposters either, they're called dishonest, but there's no "dishonesty syndrome."
So I hesitate to reach for explanations of imposter syndrome if I'm not actually qualified for something. It can become used as a crutch to fall back on like a lot of diagnoses, instead of addressing the root causes of qualification. Waking up on that cycle made me realize I have a lot to work on in some areas.