I believe the author of the article is confusing "manager" and "tech lead/senior developer". I think the author has projected things they think are important in a manager onto the roll and those things probably don't align with what senior stakeholders think are important.

I would certainly expect the technical lead to do a good amount of coding in addition to design and mentoring, but expecting the CTO to code as the article suggests seems wrong. I guess this might be true at a 25 person startup, but I think this is an unrealistic requirement for larger organizations.

By a similar argument, would the COO be reasonably expected to work on the assembly line and repair hvac on a regular basis? Again, perhaps at a company of 25 but seemingly (to me at least) absurd at a larger company.