As somebody who had a porn addiction (as in: I feel my consumption negatively impacted my life) I don't understand why some commenters here say it's "only" treating a symptom.
Sure, if I'd felt more engaged in other areas during my youth, I might not have started consuming porn. And I might not have stopped consuming if it weren't for changes in my life that prompted me to do so. But please, when treating addiction you can't try to solve all the other problematic patterns in a person's life. Often only after resolving the addiction people are enabled to address their other pain-points.
If this app -- and I wouldn't trust that thing on any of my devices -- helps people get off porn when they want to get off of it, I don't see how this is problematic. Or any more problematic than the use of apps for making life decisions in general.
There are many ways to manage one's habits and if something else works for you, good for you. That doesn't invalidate the approach chosen for the app.