Actually, the "canonicity" of off-screen events is an open and shut case. The producers can say whatever they like; they don't own the show and ultimately that call belongs to the people who do - and then, only in the sense that they approve or don't approve scripts, etc. because the studio doesn't actually care
whether something's "canon" per se
. They care only about whether they believe something enhances or diminishes the value of their property.
Canon is a fan obsession, nothing more or less. This is why it's been violated thousands of times on-screen.