I actually liked this one. Ash was just a spectator the whole time, which actually let Goh and Tokio shine without having any unnecessary interference, while letting Asahi gauge their teamwork without any outside elements. Plus, the addition of traps was a smart way to check if these guys can keep their heads in a bad spot; as we already know from the times Ash has encountered Mew, they should be able to deal with this much at least.
The 'betrayal' was just about what I expected, and it was good to see Goh insist that Tokio shouldn't give up for the sake of their friendship. Goh ended up losing, but it wasn't a total defeat for him, which is fine imo.
In conclusion: Where has this episode been this whole time??? Give us more of this from Project Mew!
Also, holy crap Gary is crushing it.