Its not reproccing it (hoj) - its giving a melee swing AND 2 extra attacks by stopping and restarting your attack as it procs - i think this is an issue with spell batching because the game sees the swing that procs it, setting your next swing to 0 time but you stopped swinging. Then you start the attack again with a swing time of zero and because of spell batching the game still registers as having an extra attack banked. Im sure if you could click the macro faster between batched (400ms) swings - you would see more attacks.
Either way, abusing an ingame bug (sit/stand should NOT be giving rek stacks and is broken like enrage/blood craze on a warrior) can be considered an exploit.
I also created a thread about this when a certain streamer was testing how it can be abused in strath UD. The thread was deleted because it was deemed to not be doing enough damage to make it worth it.