Hmm – I do this when the tyre is loose on the rim before inflation, but can only manage to get a third or half way round before things get too tight (this is on different tyre and rim combos). Also, I need to hold the tyre on the rim with one hand to stop it slipping off as I work round. To be fair, the vid isn’t explicit as to whether he does get all the way round.
Even if only part way round, it still works and closes the gap enough to get the inflation process started.
I use a tube to seat one side properly first and then inflate tubeless with tube removed, which means you’ve won half the battle. The other option is to put another layer or two of rim tape to close the gap…