No. You do not HAVE to meet him and hang out with him or be involved with him in any way. Nobody can make you.
To me ethical polyamory means everyone is consenting to be there -- it's not like secret cheating going on. Easy enough to me to do a 5 min call or email exchanging contact info and that yes, I am aware and I am willing to be here. That is all it needs to be.
Besides, should something happen to your shared sweetie, then whoever she was with can call the other one to let them know. That's considerate.
Galagirl