I just tested this in v3.284.10 to this same issue
This looks like it was actually a broken feature for a bit, so development took it out of the product until it worked properly. I found this community page helpful as Darren talks through that process. Not possible to reorder pages - #23 by Jeje
The good news is that it is fixed in newer releases past your version. Darren mentions versions past v3.291.0 should be good to go!
In the meantime, you should be able to use the AI Assist agent while editing the app and ask it to re-order your pages for the time being. This should at least remove the manual effort for now until the upgrade takes place.
Let me know if you have any further questions or concerns on the topic.