i agree he was trying to put luke off. maybe he did have some training in the temple, i dunno. but regardless, i think something has to happen that creates in him a sense of loyalty to the cause (either to obi-wan, or to the rebellion, or even to luke). otherwise, why is he involved? something must happen that sparks his willingness to get involved in the whole deception. he must have known, too the dangers involved in hiding vader's redemption (hey, there's a cool title 🙂 )
maybe