As jerf said, it's always difficult to see if an implementation of a protocol respects it completely. Most of us trust OpenSSH because of its background. It's old enough, the codebase is mature enough and maintained by the OpenBSD team. However it's quite a massive project, I don't know how they would be able that their implementation fits completely the 6 RFCs, I mean, more than the go implementation.

In our case, the SSH server is not for general purpose, but for something really specific, so it's really easier to test. What other feature? As I will explain next week, our SSH server is actually an authentication/autorization proxy which forwards connections to another server. By building our solution, it is now easier to control the logics for the load balancing etc.