The weird thing about GameXplain's behavior for me is that if they sincerely believe (or know) its fake, they can simply use the evidence surrounding the background dug up by folks like Vaanrose and ArtsyOmni as the main crux of their argument against the leak without mentioning anything about whether they believe Incineroar or any of the characters on the banner would be newcomers. Them simply being Team Fake is one thing but refusing to discuss it at all makes me feel that they either:
-Later found out that its true after their initial video and can't go back and say the leak is true as that would be suspicious and aren't going to lie and pretend its fake.
-More likely, they're Team Fake but not 100% sure of it being fake and don't want to end up with egg on their face like what happened after the ESRB leak.