> The number of Unicode scalar values in the string. It's the basic building block of Unicode.

No, codepoints are, hence their name. Scalars are a subset of all codepoints. https://stackoverflow.com/questions/48465265/what-is-the-dif...

> whether that's "UTF-16 code point"

That's not a thing; you're thinking of UTF-16 code units rather, I believe.