I don't know of any active hunter that is going to deny the third party apps exist. They've been there all along. They're a dual-edged sword - they both help and hurt the community depending on how the individual user uses the information. Ignoring their existence is futile.
But it's not the apps that are causing S ranks to die in seconds. That's a result of the game's power creep. SE needs to address that problem if their goal is to make certain that hunts remain accessible to players of the intended level. If SE addresses the problem correctly, it's not going to matter if someone is using a third party app to get instant notification because the hunt will not being dying within seconds.
As for being impossible to know where a S rank is going to spawn in advance, that's false. All you have to do is track where the As and Bs have spawned since the last kill. Players have been doing it that way since they figured out that the next spawn location is reserved at death. The tracking websites make it easier for hunters to share the information but it could still be done with pen and paper if one wanted to. Not trying to say that's how your troll is doing it (clearly they're using the third party app) but it is not impossible.