book authors trying to seem smart

I’m reading a book about the history of mathematics, and there’s a section about the discovery of irrational numbers. Pythagoras proved that the square of a number can never be equal to twice the square of another. The book says:
“But the square root of 2 is obviously a ‘number’ of some sort*;”

The foot note says:
“The inherent visciousness of such an assumption is obvious.”
Whether it’s obvious or not, if the author believes so, why even mention it?

Note, also, that the FIRST PAGE reads, “…it is just possible that Archimedes, could he come to life long enough to take a post-graduate course…”