The relevant section is about programming style, not efficiency or performance.

Oh, its 'style advice'. It's perfectly fine to cargo-cult that(*).

Does the book have any opinion on whether I should be wearing a full beard with my knee-crutched jeans or just 3-day stubble?

(*)My point being, that you are still passing on information you have read, as advice or preference or law, without having examined the reasoning behind it, or having applied your own reasoning to it; or concluded that it is good advice, preference or law on the basis of your own experience.

I occasionally suggest or recommend the use of strict and/or warnings. I do so, not because I've read that they should be used, nor even because someone told me it is a good idea; but because I personally have found them useful to me. And when I do so; I demonstrate what benefit the OP would have accrued from doing so.

But nowhere have you even attempted to reason (beyond "looks a bit clunky"; and you read it in a book) why you think my use of map is suboptimal. That's cargo-cult.