The supernova was already canon. He isn't canonizing it.
Ugh. Not this again. CBS can say things are canon, but that doesn't mean future productions will respect that. TAS is such an example, and I'm sure you can find things in the movies or TNG that contradict/ignore elements therein. Furthermore, ST'09 itself ignored (or took major liberties) with established canon. Why is Pike about 10 years older in the Kelvinverse, when he was born before the timeline split? Why is Kirk's mom -- who is on the verge of giving birth -- on a starship in deep space before the timeline split, when canon establishes Kirk was born in Iowa? etc...
All I'm saying is that if Kurtzman is obliged to uphold CBS canon, he has to include Sybok.