You mean he pulled him through the force field? Sorry, I don't get the scenario you're trying to describe.
I think what he's saying is the Sorc force ran and jumped out of the first spawn when defending and pulled sniper to him on the top of the middle partition. I've been up there and it's over 30 m to the doors. Maybe a marksman sniper could still reach them but I seem to remember targeting people up there and they were 40 m away when on the doors.
And btw I wouldn't consider this an exploit at all, just a wise use of map design, if that is its even possible. Personally I just jump up there a lot at the round start to get a birds eye view on which door they're hitting.
And it's pretty useful if your pugging and you quickly notice too many went to defend one side. Pick out a high priority on the other side force pull up ( as a TankSin) then KB to the other side. Presto, numbers are evened out.