If possible, I'd suggest he talks to doctors who are still in training posts (junior doctors- anything below consultant/fully qualified GP). Medical students can explain what the course is like but even they often have little idea of what it's like to actually be a junior doctor.
The first two years are changing departments every four months and not uncommon to change hospitals as well. Once in specialty training change hospitals every 6-12 months with little to no control over where in the country you work. Gruelling rotas that leave you with no time/energy outside of work. Constantly feeling like you don't have enough time/staff/resources to do a good job. During day to day work doing more admin than actual medicine, then being expected to manage seriously ill patients without supervision/support on nights and weekends. Being refused annual leave for important events. Having to pay thousands each year for GMC, medical indemnity, BMA, portfolios, training courses, exams...all of which are mandatory.
GPs are doom and gloom for a reason, but at least they're finished training and have a permanent job and no longer have to move around frequently. Junior doctors have it even worse. And with the recent changes to applications for specialty training (including GP), it's now more difficult to get a training post, so excellent doctors are languishing for years in "clinical fellow" or "trust doctor" roles, with no chance for career or salary progression and often the worst placements despite their level of experience.
I know I sound like I'm trying to put your DS off, but I wish someone had told me this when I was applying.
If he hasn't already, reading Adam Kay's book "this is going to hurt" and the BBC series based on it is really useful- the most accurate I've read/seen.