Oh whoa. While I was reading
this research, got another EX pass. This will be my second time for an EX raid.
Anyway, it's late at night nearing morning, so I'll need to stomach the research again later... but reading that research, it can now be said that Niantic is lying on one of the criteria that heighten the chance for EX invitation; Doing
more raids actually gives
LESS chance to get EX passes. Other criteria such as gym badge tiers also seem to lean toward
LESS chance, although this is not statistically significant enough to be conclusive yet.
EDIT: Oh great... people in the comments also discuss about how they also seem to have lower chance to get EX pass with Gold gym badges although, it is not statistically significant yet as aforementioned. And coincidentally(?), I got that EX Pass on silver Gym, while the Gym I have Gold on doesn't give it or doesn't host EX Raid this time. Just Great, since I have ground so much for two of the EX Raid eligible gyms to Gold.
Either way, what a scrap show, Niantic. You actually screw up EX Raid so much, the community actually had to do research on it and proved what was announced to be Tauros scrap. Very well done. Truly the
best example of Scrappy Mechanic ever.