It seems unclear to me how "point" of origin is defined on the OWE fares. Are co-terminals part of the same "point"?

Basically, is this allowed:
JFK-SYD-......-LHR-EWR-ORD-LGA?

I'm not technically returning to my airport of origin (JFK) by transiting through EWR to ORD (I would like to do this to return home for a few days mid-trip), but if the OWE rules consider JFK/EWR/LGA the same point, clearly this violates the rule about returning to the city of origin.
Does it matter if EWR is a transit with or without stopover?

Thanks!