I can only speak for myself but for me, it's all about the syntax. I am terrible at recalling the exact name of all the functions in a library or parameters in an API, which really slows me down when writing code. I've also explored all kinds of programming languages in different paradigms, which makes it hard to recall the exact syntax of operators (is comparison '=' or '==' in this language? Comments are // or /*? How many parameters does this function take, and in what order...) or control structures. But I'm good at high level programming concepts, so it's easy to say what I want in technical language and let the LLM find the exact syntax and command names for me.
I guess if you specialise in maintaining a code base with a single language and a fixed set of libraries then it becomes easier to remember all the details, but for me it will always be less effort to just search the names for whatever tools I want to include in a program at any point.
I agree with a bunch of this (I'm almost exclusively doing python and bash; bash is the one I can never remember more than the basics of). I will give the caveat that I historically haven't made use of fancy IDEs with easy lookup of function names, so would semi-often be fixing "ugh I got the function name wrong" mistakes.
Similar to how you outlined multi-language vs specialist, I wonder if "full stack" vs "niche" work unspokenly underlies some of the camps of "I just trust the AI" vs "it's not saving me any time".