Sorry, no, that does half the job, but only half the job.
It’s shuffling up all of the overrides, but leaving all the Master Page Changes where they are, thus causing an irritating but fixable problem. In 38 pages I have 16 Master Page Changes - mostly “firsts” to “defaults” and back again, but with the odd custom page thrown in for good measure.
I’ve dug through my backups (both in the Dorico backup folder and on iDrive - thank goodness for continuous data protection and versioning!) but also constructed a list of Master Page Changes to “put right” after deleting the blank page.
As an educational exercise I went through and recreated all of the muddled Master Page Changes and (thankfully) everything I’d hope to remain intact has remained intact (it really is just the frames that moved, NOT any of the carefully-tweaked music flowing through them).
The question still remains, though: how does one go about removing, say, 32 bars halfway through a multi-flow layout without all of the following pages messing up?