I can’t figure out yet what Marty’s return is meant to signify. I can’t say he came back to cause friction between Logan and Rory because I think that’s what the TA is for. I don’t think Marty would drop any innuendos to Logan about Rory’s crush on the TA because how would he know about it; certainly not from Rory. After the fiasco of keeping their friendship secret from Lucy, I don’t think Rory would trust him to tell him about her feelings for the TA and I would certainly hope that Lucy or Olivia would not betray her trust if they knew about it.

Marty’s only connection so far with Rory is through Lucy and if Rory and Lucy are going to remain friends, maybe the purpose of this SL is about Rory’s ability to build new friendships/relationships that are based on honesty and trust and not being afraid to be true to herself in the face of adverse/problematic situations and confronting them instead of running away from them???

Maybe Logan himself overhears Rory sharing her confidence with Lucy or Olivia about her feelings for the TA.