I think wires are indeed crossed, as others have posted on this site that your medical has to be issued in the UK if you TRAIN in the UK
However, can I just urge people not to waste money having an unnecessary medical? Unless you have complex visual problems or are colour blind, the chance of failing a medical at this tender age is zilch unless you have previous medical problems such as asthma. And if you do, a letter or email to the regulator will be free! and give you the information you need to decide whether you can pass or not.
I regret that putting you have a medical on a CV wont count for much. But I hope your son succeeds with his ambition