It's not "purposefully convoluted", and I'm not talking about "normal development experience", but rather the larger amount of non-essential complexity it shows; and as anyone should be aware, complexity is always an opportunity for bugs, regardless of whether it's something you would see or write or even be aware of in the "normal development experience". Combine that with Apple's attitude of constant churn and it's not hard to see how bugs can multiply easily.

Using a C++ library from C is not hard because objects map to structures in a straightforward manner (and in fact early C++ compilers were C++ to C translators), and you would need to use structures anyway, unless the library was obtusely designed with nonessential complexity. That's how the Win32 API works too (with the exception of the bloated COM stuff.)