problem with "lock frame"

I’m just asking for some improvements with frame and system breaks. I would prefer, if using these functions would take existing breaks into account. I create al lot of collections with a lot of flows and very different pieces. Therefore I often don’t know in the beginning, what I will need in the end.
Dorcio seems to calulate systems and note spacing different, when it calculates a whole page or e.g. just the last to systems of a page. Dorico adds systems breaks, when you edit the note spacing. When I change the note spacing e.g. on a page with 6 systems in system 4, Dorico often changes the layout of system 5 and 6, where I get more bars in system 5 and less bars in system 6. Therefore I need to lock these systems and locking the page is the easiest and fastest way to do this. And when I - as in my case - need to set a frame break on page 3, because I want to change the staff size, I don’t have a choice not use a break for this.
What is the point of having these great lock functions, when one can’t use them in many cases?