It always does, imo.

Not always. Sometimes it's just amplifying the devil's arguments by repetition. Time and place, and all that jazz.

The initial exaggeration was probably unintentional, due to second-hand eyewitness testimony getting relayed as fact in the middle of the chaos. But it was later used to pretend nothing happened, which clearly isn't the case. My girlfriend is Chinese and has no idea anything ever happened in Tiananmen Square: she didn't even know that date was censored online, so whatever they're doing is working very well.