because you have to log the place of embarkation Art 35 and if its not licensed, you will not be able to claim that flight for licence issue.
You can bet your life the student will log the entire flight time and put the intermediate licensed aerodrome as the point of embarkation and disembarkation. Nobody will ever notice unless they look at the Tech Log! Now if there is an accident, it will attract attention and an insurance company may well try to opt out of paying, by claiming that part of the flight was illegal!