Our experience with IBD is that the Humanities kids like it but for the more mathy kids the math just isn’t robust enough, and isn’t timed right for them. So those kids end up dropping the diploma and taking Mvc or similar at a local college.
And yes, I know in theory the IB HL math can be stretched to fit. But in practice it rarely makes sense for a school to do that for the small group of math whizzes.
Anyway, colleges are fine with it either way.