Tiled 1.9+ uses the existence of "regions" layers to determine whether Automapping rules should always use the old behaviour where tiles that are empty in all layers behave as "Other", allowing old rule maps to behave correctly in 1.9+ instead of breaking. However, a major difference in 1.9+ is that rules are executed out of order by default, while in older versions, rules always executed in order. This means that old rules are still likely to run incorrectly in 1.9+, and users have to update their rulemaps even if they keep their "regions" layers.

In the interest of backwards compatibility, I think that if a rulemap has "regions" layers and does not have a specific value for MatchInOrder set, MatchInOrder should be treated as true. If there is a specific value set, that value should be used.