I am not convinced this ever happened in any meaningful sense. As you note, it turned into armed conflict almost immediately. This was a British-induced transient state that was unable to sustain itself in the region.

> The “settlers” were the British and they left.

The Myanmar state/people are also colonizers/conquerors. You don't need to come across an ocean to see territory that you dont control and decide to try to take control by force. Facebook and ethno-nationalism are simply new tools in a long-running conflict.