It's canon, but it doesn't matter until it appears in any WoW media, which it hasn't and probably never will.
It didn't appear or get mentioned in Sylvanas, the one time it would really matter, and in fact it kind of hints that there are multiple Jailers or that there are multiple timelines: Zovaal knows Sargeras will hit Azeroth with Gorribal.
How would he know that without watching another timeline? Unless he told Sargeras/told Mal'ganis to tell Sargeras to do that, but I highly doubt that.