I just watched the movie, mashallah. I don't think this was a mockery, he didn't just try to copy he copied in an attempt to learn and understand better. And if you''d watch it you'll see he did learn a lot from it.
Obviously he didn't "just carry on" afterwards as it was never his intention, He didn't do this because he wanted to becoem muslim, he did it with teh only intention of leanring. So there's nothing hypocrite about "turning back" afterwards. In fact I think he is very sincere to God, you should have seen how afraid he was to follow the prayer. It might seem stupid for someone who takesit for granted, but Imagen for a second that you're in a position where you're asked to follow a christian prayer and state: in the name of the father , the child,and the holy spirit (astagfurallah).
Anyway did they ever do a follow up on this? Wonder if he continued studying qur'an and such.