Is this nested ticketing?

All of these trips would be credited to my SkyMiles Account and all would use GUC’s. Each trip is booked directly with the airline being flown.

Trip 1 outbound, ticketed and flown on a SkyTeam Partner. JFK-CCC with a connection at BBB.

Trip 2 outbound, ticketed and flown on DL. CCC-EWR with a connection at DDD.

Trip 2 inbound, ticketed and flown on DL. EWR-CCC with a connection at DDD.

Trip 1 inbound, ticketed and flown on a SkyTeam Partner. CCC-JFK with a connection at BBB.

If this is nested ticketing, would changing EWR (co-terminal to JFK) to BOS/DTW/??? cure that?

(The gyrations we go through for MR’s amaze me.)