Zombie Sion can Ascend and Revive

Not sure if its supposed to work this way but, while I was playing ascension, our team killed the Sion before he was about to receive the ascension buff. He turned into his zombie form and ended up getting the buff and completely reviving. Again, if its supposed to work that way its fine, but it just seems weird that a "dead" champion could still receive the buff and be revived from it.