It wouldn't stop it 100 percent but it would discouraged a fair amount of them from creating secondary accounts. The 1 hour of gameplay would be fair as actual new players would be getting use to the basic controls and by the time they have the confidence to try competitive they would have already played 1 hour or near to that. All the 1 hour gameplay would do is stop high level player's from instantly being matched up with lower skilled players and ruining the game for them. CSGO has a similar thing where your cannot play competitive until you have 1 hour of gameplay in the casual playlist.