When I had my hobby shop I taught many people to fly with the Senior and Seniorita. In my experience a beginner will solo faster without ailerons as that cuts down on the number of things he has to learn all at once. When you solo and start to get some flying time on your own you quickly build the reflexes you need to keep the airplane under your control rather than chasing it around the sky trying to keep it from going out of sight or into the ground. When you get to that stage it is easy to learn how to steer it on the ground with the left hand. A lot of instructors while meaning well forget what they went through when they learned to fly and they want your airplane set up the way they like to fly it. The poor newbe then gets overwhelmed trying to operate both sticks in two axis all at once. While you are first learning it is hard enough to operate one axis on one stick. He will concentrate on the right hand trying to steer initially and you have to remind him to ease off the rudder to keep it from diving then remind him to use elevator to maintain altitude then get him to roll out on the desired heading. The mind will concentrate on only one thing at a time initially and nothing but repetition will help that. When a throttle change is needed the right hand is temporarily out of the loop while the left hand moves the throttle stick. The ideal trainer takes care of itself while you figure out what you need to do and is moving slowly enough that you can find it again when the mind shifts back to the watch mode. This is what I have discovered in 50 years of teaching and the Senior and Seniorita fill these needs as designed. So even if the instructor says you have to have ailerons to learn how to fly, know that you will get to that important solo stage faster without them.