That's a really long article to say what we already know: That "expert" means to know in detail a narrow thing.

It hasn't been possible to be a true polymath in like 500 years. Surely this isn't news to the author?

There's no such thing as "an expert on everything"? Yeah, no shit. It's almost tautology, due to the limitations on human brains and the advancement of science since the renaissance.

Another way I think this article misses the point is that they're not dragging Sundar in front of congress because he knows everything about Google (he can't), nor for the congresspeople to learn it (they can't, even if Sundar knew, and could convey, and had infinite time).

They do not start from "let's understand everything first", because they can't. They are dragging them in to answer a question.

You don't need to know the lunch schedule of the San Bruno office, or how many registers the x86 processor has, to answer the question of how political ads should look in today's world (or whatever the question is).

So the article doubly misses the point.