I understand it's because they'd find it an interesting degree (although, even as an accountant, that slightly bemuses me) but I'd then have found it a bit boring to re-cover the same stuff for the formal accountancy qualification (appreciate you may get some exemptions in the first year).
I have to echo this - and I have read all your posts explaining his view. I get wanting to do a degree but I think he will regret the subject choice. I support our graduate trainees in my current role, so I'm not opposed to a degree route in principle (although as pp I would always check that someone asking your original question knows there are other paths as people often don't realise!).
When we have grads with accounting degrees they get bored and frustrated having to go over the same ground for exams (albeit from a different angle), feeling like they're "revising" their degree content for the first years of their training contract. Whilst at the same time discovering that a three year degree course doesn't actually make learning the practical side of the job much easier than it is for those coming to it cold. The theory and the practical are very different.
Some of them get really very disillusioned whereas our grads with non-accounting degrees (even where accountancy was always the plan) are much more engaged and motivated - they feel like they're progressing, our accounting grads feel like they're stagnating. And sometimes the accounting grads get quite pissed off they've got massive student debts and yet are not even able to do the practical part of accountancy any more easily than someone who did a marine biology or art history degree.
Whilst exemptions can be available we usually don't like people to take too many (if any) because it's harder to jump into the exams at the higher levels if they haven't built up the technique and experience (being professional exams not academic exams - different technique). Everyone I've watched try to take up exemptions to skip the foundation stages has just repeatedly failed the higher exams because they didn't have the experience of how to approach professional exams. (Which is why we usually say no.)
Even if it's only a few small sideways steps away from a pure accounting & finance degree, long term I would strongly encourage him to consider choosing a different course. Define which parts he expects to enjoy and look for other options where those elements are shared. I find it hard to believe that out of all the available degrees that there is only one viable possibility for him when he is basically only doing it for fun.
There's no point picking an enjoyable degree for the degree experience if the career he's specifically doing it for will be tedious and monotonous for three years as a direct result of that degree choice iyswim. That's not a nice way to start your career and not conducive to a strong foundation for career success.