OK, we got it. You are a great instructor. But the OP's question was about whether it was harder to teach Rescue in SM (not specified if the victim or the Rescuer is in SM); the first response (mine) was Yes, it is harder.AFAIK, PADI has no problem with different configurations, including backmounted doubles. While I had a conversation with one of the training consultants about the i3 and sidemount, the response was 100% supportive.
I don't see PADI rescue as being aimed that way. As an instructor, it is my job to give the best course that I can. Teaching the bare minimum is embracing mediocrity, and that doesn't interest me very much.