Savage Love was in a very similar situation than Say So in the US. Both songs were already certified hits before the release of the remix, but the remix was released after the song had started to lose steam and only with the remix could they bounce back and eventually become #1.
In other cases like Perfect or Savage, the song was still rising when the remix was released so we'll never know if the song would have topped the charts had the remixes not been released.
The big kii here in my opinion is that this is the remix of a remix, since Savage Love itself was a vocal mix of Jawsh's originally instrumental track.