Yeah me too I think it's cannon but why is it in another dimension (timeline)? I don't get it. This should be cannon, there's nothing non-cannon about it. Ben returns home, fights stuff (as shown in Omniverse) and let's go of the Omnitrix. Then Alien Force/Ultimate Alien happens. Why non-cannonise this episode? It's as cannon and as in the same dimension (or timeline) as every other episode!