Again, it comes down to context:
- Have a layout where flows can start on existing pages.
- Invoke a master page change (because you want titles or something at the start of a flow midway through the layout).
- Override something on the frames on that page (e.g. because you want another title midway down the page).
- Fiddle with pagination on previous pages (e.g. by cutting 16 bars).
- Delete a now spare previous page (by moving to the end of layout and then removing page overrides from this page).
Step 3 - introducing an override - locks the frames on that page in their current state, and that includes the position of the (totally default) page number text frame at either the top left or top right corner.
It would be jolly lovely to not override Master Pages ever, but - and this is crucial - merely replacing {@flowtitle@} with {@flow2title} constitutes an override.
I cannot for love nor money find a way to have a new flow start halfway down a page with an existing flow WITHOUT either creating a brand new Master Page (specifically for that single page) OR introducing an override.