The section you refer to is a justification for code completion and possible providing (visual) feedback for whether a various constructs are spelled or used correctly. It is fairly established that sort of thing increases programmer productivity (as in writing a Java program using notepad vs. writing it using IntelliJ).

In the old days, we used to do this by using static type inference. This is harder to do in dynamic languages (such as Python), so now we try to do it with LLMs.

It is not obvious to me that LLMs are a better solution; you may be able to do more but you loose the predictability of the classic approach.