So basically, you'd be "punishing" someone for being honest and potentially promoting someone who is better at "manoeuvering" through the corp labyrinth.
From the boss's side, yes, punishing someone for honesty and promoting someone else for keeping their mouth shut on the same feelings is... suboptimal at best.
From the worker's side, though, you don't know how smart the boss is. You don't know whether they are a jerk or a compassionate human being. Don't give them ammunition to use against you. (If you know your boss well, and you know they won't use it against you, that's different. I've had bosses that I would absolutely trust with that kind of information. And, I've had bosses that I wasn't sure I could do that. And I've seen one that I absolutely know I couldn't trust with anything negative, but fortunately he was never my boss.)
So, yes, beware of who your boss is.