If you use plan builder in Jan and have it run through June. And in march they update the plans, what is in your calendar will not change to reflect those new plans. I think that is what you’re asking about not happening right?
You’d need to delete your current plan and run plan builder again, but you tell it to start when you did not start today. It will rebuild what’s in your calendar with the updated plan.
If your week start is a Monday don’t run it on a Sunday. I did this and it basically made Sunday a 1 day week and threw everything off. I had to delete it again and rerun it on the first day of my week and then it was fine.
It may also adjust your phases to a different number of weeks.
If you’re on the last week of a plan then it doesn’t really make sense to rebuild it just maybe find some alternates that reflect the adjusted plans.