It is normal for dogs to offer other behaviors while learning something new. This is all part of the experimentation part for the dog. For a young puppy, I keep the rate of reinforcement high. So for the perch, I start out clicking any interaction with the perch. Gradually, I increase my criteria such as one foot on. Keep increasing the criteria at a rate that is appropriate for your dog. Some give up quickly while others keep trying different behaviors. If you have one foot on, you are very close to both feet. If you find your dog starting to quit or become bored, go back a small step. This is assuming your dog has a full understanding of freeshaping (which it sounds like he does). Pretty soon, you will be able to move on to the next step of rear end movement and thats when they fun really starts!
One thing I am not sure I understand is your question of going back a step and doing nose touches. Do you mean nose touches to the bowl? Or your hand? Or?
I also love to do "get in the box" freeshaping with all my new puppies. It really teaches them how to interact with their environment and think.
Hope this helps