Why are you making normative claims about technical documentation? That seems to me more preposterous than anything written in the mentioned piece.
It also becomes incredibly boring. I hear what you're saying, but work has to be fun, at least sometimes.
To carry on with your intended meaning, what is the problem if the technical documentation is more than just technical documentation? We're talking about a paragraph here, maybe 0.1% of the documentation. Are you making a claim that at some percentage of non-technical content the documentation becomes illegitimate?
I'm honestly just trying to understand what you're getting at.