Impeymac I agree that Al Mourjan is not available to OW status passengers in Y but OW premium passengers (F and J) have full access.

I understand “Lounge access will be determined on the international long haul ticketed flight (either First of Business Class) regardless of the ticketed class of travel on the international short haul or domestic flight. “ as meaning that even though departing in Y the passenger is still regarded as a Premium passenger departing in J for lounge access and thus has access to Al Mourjan (Premium lounge). As far as I can see he would not automatically have access to the OW (status) lounges. They require OW status.

I also find it strange that short haul Y then long haul J gives automatic access but Long haul J then short haul Y does not. This is surely what the OW rule is trying to alleviate.

As you know I have maintained that it is the departure class that governs lounge access but here is an exception to that (unwritten?) rule.