I may be missing something important, but recently I had to redo my staff spacing adjustments couple of times from scratch. Any time I inserted a page before the page I have changed the spacing on (I had to add blank pages for booklet, so the page turns are feasible) - any work on staff spacing were lost.
I realize that any changes to staff layout would result in a recount, but an addition of a whole page without any music flows should not undo anything since everything offsets by a whole page anyway.
Locking flows results (as far as I know) in preventing the bars to move, but does not prevent the staff spacing recount.
I know I could have saved the staff spacing adjustments to the very end, but sometimes one needs to adjust the spacing to check if the casting-off will fit. Or sometimes there is an order for one more title page in the beginning with commission information etc.