I see your technical reasoning behind why two emtters in parallel will not work. I also see the original poster can't get them to work. Only trouble is, I have done it many many times without an issue.

In fact, I order what amounts to being a mini plug splitter, that would normally be used for two sets of headphones off of an audio device, and I use it to drive two emitters off of one port.

I did it today when the client wanted me to add an emitter to control his old Denon compact disc changer with his URC remote. It worked.

Perhaps there is something forgiving about URC base stations, or URC emitters. Whatever the case, I have done it multiple times over the years and have never had it fail.