In the case of trying to block a specific video, it could be even more effective, because as soon as that video gets uploaded, you can assume the 'new' person is the same person as the existing profile—it doesn't really matter if you're wrong because even if it's two people, you're trying to stop them both.
I'm not sure how this would in any way inhibit journalists or activists except that, they too, would not be able to upload the disallowed video to your site.
From my limited experience in this space (I moderate a tiny social app that has problems with bad actors), IP address blocking had high false positives and low false negatives.
But a false positive here just means someone can access the video who isn’t supposed to access it. Without the system in place anyone can access it.
This inhibits journalists or activists that may want to obscure their identity.
In the context of porn, perhaps the person uploading the video is the performer and does not want to attached their real ID to the performance.