Hello there!
I found this little bug 3-4 weeks ago or so.
Well basicly what happened is, I was on my way to Orgrimmar on the Wyvern, and a group asked me if I wanted to go to ZF, fair enough. I decided to join.
I was flying above Alcaz Island when I got the summon, and I pressed accept.
Which resulted in me getting EXP from both discovering Zul'Farrak and Alcaz Island.
So if you are getting summoned on your twink, it would be better to wait with accepting the summon, till you are at a place you've already discovered.
After I saw that we had no healer, I then used my hearthstone back to Gadgetzan, and flew to Orgrimmar again.