I don't understand your reactions. Maybe because I am not from the US.
People say: you should NOT hire your partner.
So, you should NOT hire friends? So, you should NOT hire people you like? So, you should NOT hire people for who you have any opinion? So, you should NOT have any hobbies other employees can have?
Our decisions are obviously biased by our feelings, and it's normal, we want people reliable, people we can trust! What's wrong with that?
In some cases, we want objective decisions. In these cases, you should just recognize your incapacity to be unbiased and let other people take the decision.
When I read the blog post, Keith didn't seem to have faced a such case, so non-disclosed his relationship seemed to have been the best decision to avoid to influence other people decisions.
It's common to meet the "love of our life" where we work, I don't understand why it should be forbidden to those who have a management role.