Kind of a load of rubbish tbh, everyone questions their choices no matter what they are. There's always going to be a point at university/sixth form/your job etc where you think "ugh, why didn't I just do X job instead? I wouldn't have to deal with this and that..."
Literally everyone. Even medicine students.
I guess what they're trying to say is that if you've got a couple of other options and you're kind of not enthusiastic about medicine, then maybe it's not for you. But they just worded it in a silly way.