It was on April 17, 2014 in a article of Devianart and Disney daily news.
Chris Sanders wasn't the only one who said "Stitch!" is non-canon, Disney did too.
Despite having characters from Lilo & Stitch, as well as getting English dubbed, attempting to connect its story to the original franchise, complaints about its changes, and contradictions toward the original film and series started. That's when, five days later after airing on Disney XD, it was cancelled.
Nope, it is not canon, Cris Sanders said that and glad to hear it (?) Some things don't match with the original films and series :') coff coff for example Reuben and Gantu reached happiness at the end of Leroy and Stitch, then in the anime no coff coff. TuT