Anyone whose crying smurf knows how to rate subtle gameplay differences which shouldn't exist within a specific Elo.
If a Silver Yasuo has you Airborne the 1/10th second his Q Tornado hits, not once, but every time, you generally know he's a smurf. Yasuos in Silver generally Ult about 6/10th of a second after an Airborne. They don't Ult at the exact same time it hits.
If a Zed Triple Shadows you in a clipped combo, he's not silver.
If a day 2 Akali goes 32/2/8 with the new champ in silver, she's NOT silver.
You're oblivious if you think smurfs maintain 70% win rates. They don't. The invest if keeping their accounts down. Although some smurfs maintain carry scores on some champs and intentionally feed on other champs, most generally just choose games to win and games to lose. Often, your 3/19/3 champs are actually smurfs de-ranking their accounts.
I actually am friends with several, and one myself, and they all do this.
If you see a Graves 0/6 early game in what seems to be "stupid" play, and then recovers to 18/8, It's VERY likely that's a smurf, because he sabotaged his early game snowball yet still carried the game..
I think you need to watch this video of Glacierr.
https://www.youtube.com/watch?v=q3np5Xl2JKU
He has a WHOLE SERIES of pretending to be low elo to "coaches" and some of them are actually convincing.
(He has a Zed one where game 1 he literally behaved exactly like a low elo Zed, and then let loose in game 2; He's obviously an awesome liar).
This is what real smurfs do.