There’s a difference between being a ‘specialist’ because you are of such a low order of insect that you are incapable of any advanced reasoning and only do what you are pre-programmed by instinct to do and specializing because you have such incredible powers of learning, reasoning, and retention that you remove a tumor from someone’s brain and save their life.
And yes, that did, and does happen every day.
But don’t worry. - It may not take any longer than a week or two to wait with a broken hand after you find one.
Do you want a surgeon operating on your brain that has never changed his child’s diaper? Or couldn’t make a home-cooked meal? Or perform simple first-aid on someone until an ambulance arrived?
I specialize in the sciences (engineering to be specific) but that doesn’t mean I can forgo other things. For example, I’m a licensed private and glider pilot and glider instructor. I enjoy cooking, construction (and demolition). The point of the quote is that some people get so focused into what they do that they forget the other things and could be useless unless in a specific situation.