I don't think so, because for one it's in a PvP BG.. and two, it can be used to effectively prevent the other team from getting their flag back (although as you can see, it benefits the Alliance far more than the Horde.)
Also, if you think about it, ANY exploration is exploiting because walljumping is a deliberate abuse of game mechanics which is then used to access areas not available otherwise.
I'd agree it's not the greatest spot to hide the flag if you are willing to use exploits in BGs, but I can see how it would be useful in certain situations.