If memory serves, the license is the ultimate source of truth on what is allowed or not. You cannot add some section that isn't in the text of the license (at least in the US and other countries that use similar legal systems) on some website and expect it to hold up in court because the license doesn't include that text. I know of a few other bigger-name projects that try to pull these kinds of stunts because they don't believe anyone is going to actually read the text of the license.

I think if they took you to court for cloning someone's voice without permission they would probably lose because this conflict makes the terms unclear.