Rek 'Sai ult + Kallista ult = reset

So I recently saw this video and at about 1:25 it shows kallista ulting at the same time as Rek 'Sai, when they were bonded by kallista. It allowed Rek 'Sai to ult, and then have her CD immediately refreshed. Not sure if this is a bug or not, but if you want to ever try Rek 'Sai support, have fun roaming the map in seconds :D.