This has nothing to do with the article.

She's just arguing that most of the purposes of code reviews should be done before the typing part of coding instead of after. Identifying the best design before investing in typing / tokens.

Waterfall has to do with the size of the loop and when the customer gets to provide consumable feedback. She's not proposing changes to the size of that loop.

I mean, we certainly are in a lot of cases. Spec driven development is waterfall, and we're all in the midst of a new experiment to see if it works. I'm not sold, but consultants love it.