As far as I understand is that when you sign up for publishing the app you say something about having the rights to do with the app what you are doing. If then you publish an app “abusing” the YouTube service, Google will probably find it rather quickly, especially once the app gets traction, and submit a report to Apple with the claim that the app is nefarious.

AFAICT, there are no up front blockers to uploading an app that uses YouTube.