> The author is making an "absence of evidence is evidence of absence" error.
Quite the opposite, the theory he's questioning has no evidence, merely a good story justifying it. In the absence of actual evidence of the motives behind these designs, you should be agnostic, which is what the author is doing.
I don't think calling it a "myth" and "mythbusting" is agnostic. If the author was agnostic, they would call it a theory. The correct conclusion from the evidence is that we don't know. The incorrect conclusion is to say that it is a myth because there is no documentary evidence.
Quite the opposite, the theory he's questioning has no evidence, merely a good story justifying it. In the absence of actual evidence of the motives behind these designs, you should be agnostic, which is what the author is doing.