[Gameplay]Ace not announced when we aced the enemy team. Sion glitch?

I was playing a normal blind pick with some friends of mine (5 queue) when we aced the enemy team and sion was the last champ on their team that we killed. Th announcer did the whole "an enemy has been slain" thing but didn't announce the ace. I checked the death timers to see that all of the enemy team WAS IN FACT DEAD at the same time, even after sion's passive wore out and he double died. We all thought it was a glitch with sion so I'm just going to leave this here~