Ouch. This won't look good. I doubt this was done to specifically block Chinese applications, as this string is just a common reverse spam filter. The idea is

Ouch. This won't look good. I doubt this was done to specifically block Chinese applications, as this string is just a common reverse spam filter. The idea is that Chinese GFW will catch it anyhow or give such impression to spammers to scare them. Allegedly suspicious TCP reset or packet losses following responses including this type of text wasn't rare up until 2010s. Legitimate traffic to Japanese websites is supposedly negligible, therefore resistance against even cutting off all Chinese IPs is quite small among savvy Japanese computer users, and so is to sprinkle this string. Searching "六四天安門 スパム" should give you general public sentiments on this method, not specific to this case. It's at most considered a mildly questionable choice.