I would agree with you if BTEC was an option, but I have some real concerns about T-levels. Firstly, they're more exam based, and students who would likely get DDD/DDM at BTEC seem to in general come out with merits, i.e. equivalent to about Cs at A-level.
Secondly, certainly locally to me, a lot of unis seem really dubious of T-levels at the moment, and don't accept them at all- even though they will happily accept BTECs (sometimes with restrictions on the modules you have taken).
If the college has lots of success with T-levels and can point to successful leavers who've gone on to destinations the DS would like, then that's a bit different, but certainly in the county where I teach, T-levels have not been successful at all for students. It's a concern for us- as a school we offer a lot of BTECs at sixth form, level, and T-levels don't seem to be quite the right replacement for 4-5 students who struggle with exams, and maybe have slightly patchy attendance.
@Fatandmenopausal Does the college offer law A-level? That might go well with business and be somewhat useful? If he likes biology and sociology, might psychology be an option? At A-level it includes a bit of biology, and is a bit mathsy, but does also include a fair bit of writing, so many not play to his strengths.
Is there anywhere further afield he could look for a business BTEC? He does sound like the sort of student who could really succeed on one.