So I am no stranger to CL, but the problem solved in the article isn't actually one that's solved by evaluating less than the whole file at once, and in fact I didn't tell anyone to re-evaluate the whole file at all in this article.

The critical idea here is it applies to long-running functions, like a loop, a server, or other things. These, when handed function objects, will not reflect new behavior if you re-evaluate a single function.

The article solves for this by explaining to intermediate programmers that there is a difference between using function objects and using vars, something that Common Lisp programmers learn too by using #' to retrieve function objects and passing symbols and using symbol-function to look up the associated function as needed.