Phase 3 is only 3 weeks yes! The reason I have an optional 7-week meal plan in the P3toLife program laid out for you is so that you can continue to eat properly and gradually break into Phase 4 during the ensuing weeks.
Even though P3 is only 3 weeks long, the shortest break between rounds of hCG is always a minimum of 6 weeks- please see my post on required hCG diet breaks here – so there are 3 weeks after P3 where you’re kind of just “hanging” if you will. So I intentionally made the meal plan longer so that you would have a structured, guided way to eat the entire period, and then once someone is maintenance, they can rotate the 7 weeks for plenty of variety long term if they choose.
I hope this helps explain that!