Presumably they are judged on their ability to perform their jobs instead of trying to read their minds and determine whether they're acting in "good faith."
And one would hope their managers do not call them "subordinates" and instead choose a more respectful moniker.
1. One example of not acting in good-faith would be spending more effort on looking like they are performing their job well than actually performing their job well. This makes it harder for a manager to judge people's ability to do their jobs
2. Another example would be spending effort to make it look like ones peers are doing #1, thus making it harder for a manager to properly detect #1.
3. Criticizing the term "subortinates" in a reply to my comment is a bit of a non-sequitur considering it was taken directly from the GP post.
This works as long as the subordinates are acting in good-faith. The primary reason why technical competence is important in a manger is to enable them to identify the subordinates that are bullshitting them.