I'm sorry, you can't argue the font choice signals banality in the same article in which you argue that readers aren't sophisticated enough on font choice to catch that serifs are supposed to signal professionalism.
He can, he did, and we're all here arguing about it, which somehow delights me.
Why not? One quality is inherent, the other inherited. The typeface was developed with banality in mind and presumably become popular because of its utility in this respect. The ensuing popularity in word processors and on the Web likely lead to the idea that it’s more professional than others.
Again, the author:
> Indeed, the stronger explanation for Times New Roman’s long reign isn’t aesthetic excellence, but practicality and inertia.