Originally Posted by london
An open relationship does not automatically mean a fully polyamorous relationship.
Indeed. To me "open" implies even fewer rules than would be found in a specifically poly or swinging relationship. That makes the sudden imposition of rules several years in appear to be more of an attempt to display ownership than in either of the other cases.
In this case, it seems that not checking that everyone is using the same definition of "open" has led to the quirk and/or incompatibility phase being delayed by several years.