-1. It's called Tosfos Shabbos
You can tosfos shabbos all you want but come shkia you can't eat anymore unless you washed already. So let's see, they wash before shkia and then keep the seudah going for for two hours until 7pm when they can start the official seudah?
Sounds like a pain. And all so that they can "rest" between mincha and the third meal.