From plat 4 to silver 3 in one game.

Just finished the last placement match (the 11th one), and i must say im confused. After playing the 10 placement matches i surprisingly got placed plat 4. I ended my season barely taking home the plat 5 and climbing from silver 3. A minute ago i played the extra placement match which should fix all the issues with people ending up several ranks below their normal rank. But alas, i got placed silver 3 after 8 wins & 3 losses. Is this really how flex is going to be? I mean, i guess i can grind my way up to plat in flex, but im thinking about the silver players who play against players with equal skill, and here i come, like a smurf ruining the game for those players.. I Refuse to believe that will be fun.