Probably a bad professional move for him to write this post and burn those bridges. It's suspicious that he didn't describe the execs interview. Normally when I've had a good technical interview the execs interview feels like just a formality, or it turns into them selling me on the company. The one time I saw a higher up override the technical manager was when the exec had a bias against consultants. Canonical being an open source company I imagine that more wishy-washy "values" criteria are given more weight.