My first guess is that new versions of videos can be uploaded if they're similar enough (not sure how it would judge that? visually???) and/or are updated shortly enough after upload.
Edit: Oh, I didn't even see the time travel reference in the ID. Maybe the ID is generated from metadata, and there's some endpoint where he was able to throw random metadata at it in an automated process until it came out looking somewhat like "delorean". Or he was able to get ahold of the algorithm locally for a quicker version of that process. In any case, I doubt he backwards-engineered anything.
Edit: Oh, I didn't even see the time travel reference in the ID. Maybe the ID is generated from metadata, and there's some endpoint where he was able to throw random metadata at it in an automated process until it came out looking somewhat like "delorean". Or he was able to get ahold of the algorithm locally for a quicker version of that process. In any case, I doubt he backwards-engineered anything.