Well, even under that system, Plumenail seems to have figured out how to attack without extending until after the start of the lunge. Evidence from the 1996 Olympics Men's Foil gold medal bout: There are still good reasons to extend before starting the lunge, especially for a beginner. The coordination of the arm and foot on an attack are difficult and requires a lot of repetitions. But even fairly early on, maybe not in the first introductory class, but usually in the student's first year, I see coaches teaching students to vary the the coordination of the arm and foot on the attack. This blog post summarizes some practical applications with the current convention: https://www.coachescompendium.org/BENTARM.HTML. Even if the convention for foil right-of-way were much stricter about the extension, varying the timing of the extension would still be important to prevent the defender from being able to time his parry. The clip with Plumenail is a good example.