What does your friend think will make going from one bike to another so distracting that your brain will overload if you get clipless pedals at the same time?

It's just riding a bike. In the beginning, you only really have to think about clipless pedals when you're getting ready to stop, and after a few rides it becomes second nature to rotate your heel outwards before trying to put your foot down. It scares me to think there are people with drivers' licenses who find clipless pedals too difficult to figure out.