Hi Hamish and sorry for the delay.
Yes, the "auto-load" new map feature only works when only one regular map is displayed.
After some changes made following the post your refer, now it also work when you have one or multiple layers above.
But it still request only one main map (the one that will be replaced), in order to keep things clear and simple for the user (if you have multiple maps displayed and some of them start to change as you move the map, a lot of users will be confused).
If you need to deal with multiple maps covering multiple areas, you can always display them together:
https://www.alpinequest.net/en/help/v2/ ... _selection
Or use a favorite set for each base map (and multiple layers):
https://www.alpinequest.net/en/help/v2/ ... s_and_sets