Apparently something similar is used by Chinese customers reviewing restaurants. They would make a food sign from food pieces that spells "crap food" in slang, but otherwise leave a stellar review for the restaurant.

It sounds like they're hesitant to leave a bad review, why is that?

How does this help anyone?

The suggestion is that negative reviews are suppressed. Communicating a negative review through a facially positive review would help avoid that.

But this is a negative review that is literally not hidden, to the extent that it is being discussed openly on a site about a completely unrelated topic.