If you have a look on web.archive.org and search for http://www.cometpingpong.com/robots.txt you will see that there's no app directory on the May 3rd capture, but it's there on the next one on July 29th. So some time between May and July, the app section was built. Not sure if this helps someone to maybe track down who built it or find any links or mentions of it between those dates.

https://i.sli.mg/iWwYnc.png