I think he meant to bring out defensiveness with that quip. He never says that it's a big deal, just that it's the worst way to get the length of a string containing emoji, presumably of the mainstream languages.
You can’t use that information to know how much actual space it takes (in storage) as nobody sane stores UTF-32, you can’t use it to know much much logical space it takes (aka the user’s interpretation), you can’t use it to know how much visual space it takes (not that you can ever get that), and you can’t use it to segment or process the text.
A length in codepoints gives you nothing that’s really actionable, at least not that you’d need outside of a context where you could easily obtain it otherwise.
That’s… not useful?
I can’t say I remember ever caring knowing how many items I would be getting during an iteration[0]. If I want to set an iteration limit I can just… do that, using `islice` or some such.
[0] in python anyway, in lower level language there can be a utility in order to pre-allocate an output collection
Not often. There’s almost nothing useful you can correctly do with a sequence of code points.
Maybe it should just return None because the only useful thing is probably how much "space" it occupies on screen in a fixed-width font, but that's too difficult to know.