If you bought a license to use a specific Audio. And then uploaded that Audio. That audio file is still copyrighted. But you have a legal license to use said Audio. With that being said, Copyrighted Audio will still continue to be uploaded even as the platform continue to evolve.
All you have to do is make sure you have the legal rights to use said Audio. Even the Audio Roblox has uploaded is copyrighted. The point you made was to stop the copyrighted audio that is unlicensed from being uploaded. The sad part is even the terms of service says you need to have permission to use copyrighted material, even though Roblox will still moderate the audio file that you had permission to use.
So the problem lies deeper than bypassed audio. Its a problem with the moderation itself, And to fix this issue of the OP you have to dig deeper. Thus my points and posts were not irrelevant.