I tested this with a Zorua and a Gengar against Black Belt Jet Li. Whenever I lead with Zorua (disguised as Gengar), the AI used Close Combat against it. Whenever I lead with the actual Gengar, the AI used Swagger (other moves do not affect Gengar). It doesn’t seem like the AI gets tricked by Illusion.
I don’t think so…
I just tried Jet Li using illusion to make it a Gengar, Spiritomb and Noivern…it still used close combat with all…so I think you are correct in saying it doesn’t trick the AI.