season4 rank placement game BUG?

so i was playing my rank placement today and my friend messaged me stop because the is like a bug or something. before s4 begin he was with a S5 mmr and he finish his placement with an almost perfect game score 9win 1 lost but he only got placed in to S4. then i quickly did some research and find out this did not only happen to him but everyone. some G2 player finish 10-0 and get placed in to S1. some D1 player went 2-8 and got placed in S5. i mean even if he went 2-8 he should still at least be place in gold. he was D1 last season... these are only some few example and there are more. i hope this is a bug and riot decide to fix is soon. if any of friend finish placement and got placed in a ridiculously low tier please post your last season tire, placement game win and result tire on also so we could figure out what is happening. thanx