I don't use Go, but I had the exact same reaction; C is the source of most of the problems and this is just codifies the use of C. The whole thing has a security by obscurity smell.
Your comment seems to conflate a language with an ABI. To what end? What is inherently insecure about the C ABI? Why is using a syscall interface any more secure?
The C ABI is influenced by C's type model, but so is OpenBSD itself. There is no truly language independent mechanism. If a programming language implementation can't interface with a C ABI, how can it interface with the language independent mechanism?