My understanding is that copyrighted content on Youtube is often uploaded under the guise of anonymous users, but this is illusory. Unauthorized videos are taken down with vigilance, we see this happening to content creators all the time for no good reason. If these videos get the thumbs up to stay up, they're in cahoots with copyright holders somehow (most likely) or are deliberately ignored for some other reason. One think you'll notice is that not just corporate sponsored content is region-locked; sometimes "anonymous" user videos get region locked. That is not a coincidence.
All of which to say, I expect this to be the same case on PH. There's the usual wackamole game of unauthorized content being taken down, but much of what stays up from unauthorized sources probably does so out of permission that is not apparent on the surface.
I think streaming companies place a premium on the appearance of content coming from users, and this is the result. If I'm right, then changes may not significantly alter the level of traffic to PH, which is what everyone is soothsaying about: that users will just go elsewhere. But I'm curious what's going to happen.
Like you said, PH's model looks to ape youtube's, and the latter does not appear to be entirely reliant on "stolen" content.