I don't agree with this at all, and I am a developer. Of course you want to hear what you can do to make your product better, but constant criticism with no reinforcement of whats good can wear a person down.
Not to mention, in an instance like this the compliments can help further the game. They aren't just empty comments of praise, it's telling them what people really like about the game which gives them input on where to put some focus for the future.
Criticism is key in making a product great, but praise is just as important if you want your product to be well rounded.