if you are accustomed to rigid bike shoes - flexible running shoes could lead to problems
???
At a minimum, the muscles of your feet will probably need to develop some strength they lack. With flexible running shoes and platform pedals, there is an exertion required in the muscles of the foot that may be unfamiliar.
Since the large pedals distribute the pedal force without a sharp pressure edge like old metal pedals, it needn’t be a problem. Just a matter of conditioning, at least in my experience.
Otto