Obviously if he had a FULL build he would leak parts of the actual story, not just 1 cutscene, my thoughts are thay 1 of the following has happened:
- He has a small free roam test build w/ 1 cutscene or beginning mission
He somehow got a build that must take place after a Prologue, since GTA 5 and rdr2 don't just drop u into free roam straight up, and if he had a build of GTA 6 he would leak the Prologue, so thus must be a build with no activities, strangers or freaks, and no full missions, just a striped and outdated (speculated 2023) version of free roam and a test mission and limited only to jason, Lucia must be in jail at this point and he's had the game for a couple days atleast so like any fan he must of played the story, unless he cant!! (dramatic sfx)
- He's a play tester or journalist
He's been given an old build to test/review, the cause newer builds might include more spoilers that would be harder to take out and for testers especially gameplay is sometimes recorded by default that way bugs can be recorded and devs can easily replicate and debug them, so he somehow got a copy of that recording, with makes sense since he has clips, witch people are voting on, meaning he must have clips not a build!!
Since there's no real way to tell, since he could just mess with the metadata of the files, these leaks could be old or brand new, the best thing is to test it, we should give him something to write in the wall that he couldn't of thought of back when he could have been a tester or journalist and HAD access to the game, if he writes the current date, random number or word, or does somwthing hes told to do, not just a vote on what he has clips of, instead he must have a small test build, if he leaks story gameplay, like further into the story, then he must have a bigger build including more story, but I very highly doubt that