The trouble here is not that the age checking is right or wrong but it would be unethical for anyone who has the competence to develop this kind of app to work on it because it is fundamentally unworkable -- it would be like me taking money from somebody to help them with their perpetual motion machine.

The kind of developer you are going to get is either going to be somebody who knows what time it is and cynically works on a project that they know is going to fail (unethical) or someone who is not going at it with "the end in mind" but is just cosplaying as a software developer (incompetent)