If a Master player makes a new account and places Diamond, then they have an unfair advantage over players actually at Diamond level.
According to the game’s own reporting system, that’s cheating.
And, as I noted earlier, Jeff failed to acknowledge the impact such a player has in every match they play in until such time as they reach their usual SR level.
As I’ve also mentioned earlier, it’s not as simple a case as just being good at the game.
Of course a high level player on a low level smurf/alt/whatever is going to be “good” because they’re playing in a rank that they shouldn’t be in. That is the issue at hand here, and that is something that Jeff and Blizzard have failed to address.
Smurfs should only be matched against other smurfs.