It’s not the physical position on the displayed sheet. It is the order they appear in the file. I’ve successfully renumbered sheet pages by hand editing the schematic file. I wouldn’t suggest it though, it is a pain in the sits-upon and prone to error. And, I’ve had the program re-shuffle the sheets on subsequent saves requiring repeated hand edits.
Best bet is to upvote the issue on Launchpad. I would, but I already did a while ago…