Unfair is accurate. I don't need to fluff up my adjectives to satisfy some quality threshold in your mind.
I believe it is an unintended aspect of the warzone. Much like jumping over the gap. Much like the double stealth. It brings in an element of clearly unintended unbalanced play and should be fixed. But that's different than an exploit.
Jumping the gap could be countered (having someone from your team jump it, or respawn to prevent the cap), and the double stealth could be countered (spam aoe's around the doors) - the only counter for this, is to hope that the person on the other side isn't a sage/sorc and if they are, that they run out of force. (or abuse the other exploit that was previously mentioned) That is why i call it an exploit. Kind of like abusing the ramp in voidstar, to cap before the round started was an exploit - there was no way to counter it.
Either way it's against the TOS, "Disruptive behavior includes but is not limited to conduct which interferes with the normal flow of gameplay..." because it interferes with the normal flow of the warzone. Once every enemy on your side of the wall is dead, there should be no issues dropping the barrier and progressing further in the warzone.