What do you mean by “gains” exactly? Geiger +1 might not give you a PR in the workout itself, but assuming your power zones are set up correctly, it stresses your body in a way that will push adaptation and growth.
Exactly. You’re training and growing your energy systems, not playing whackamole with your power curve 
Whether your workouts will give you a new PR depends on your training history and how recently you increased your FTP setting, but literally none of them are designed to do that on purpose. The only workouts that even tell you to push to failure are the FTP tests, because everything else is about endurance and sustainable strength and repeatability.