I would imagine that if someone is hiding some use of the Grindr app from their S/O, they can be blackmailed. It would be particularly evident due to the location and photo-based tenants of the service. That is exactly why they ask the questions they do on the counterintelligence polygraph
Right, but certainly the same applies for any app someone might use to cheat (Tinder, Facebook, etc). I don't understand why Grindr is in a class of its own.
Because it’s use implies Homosexuality, which may or may not be known by the SO. Most SO would forgive cheating with the opposite sex before cheating with the same sex I’d imagine. It’s an extra layer of uncertainty.