Statement's a bit questionable imo. Yeah you can have a 33% uptime, but how does that translate into practice? You'll want it off cooldown for heavy hitting abilities, meaning you're already getting a much lower uptime than 33%. And sure, some bosses (Kromog, Flamebender) have these timed so you can go through the entirety of those abilities in one Fade, others like Gruul and Beaslord have a time gap between them, so you'll likely only end up Fading 1/3 or 2/5, or something of the sorts.