Every event? You must not be looking at very many, because the ones with the PPorg OT are actually a small percentage of the events we have in the Gallery.
You're probably looking at Dream World and Dream Radar. Maybe you haven't used those features before? Because the OT of the Pokemon obtained from there are the ones of player who obtain them. The ones here were obtained using the save file(s) that I started for the purpose of cataloging such events.
Furthermore, EACH of those pages states, "The details for these specific files are displayed, however PID, OT, ID, SID, Nature, Ball, and Nickname are variable" right at the top of each page.
Also, I'm pretty sure our info is the most accurate of the sites that do event coverage. We do occasionally make mistakes, but they are usually pointed out and fixed. I can personally vouch for most of the Japanese events we host.