Did they changed placements mechanic?

I made a smurf s4. Played 10 games and got into gold I, just with the base MMR, climbed into plat V, in season 5 won 8/2 and got into plat IV. Main account in todays placement: 7/3 - Silver I from plat IV. Did they changed anything since last season? Am I in a low elo but with high MMR?