the wins of teams they've played. Beating a good group of 5 team actually helps SOS, but we all know group of 5 wins aren't as good as power 5 wins. Likewise, beating a power 5 team that has a nice record but doesn't win a division or a conference also is nice.
By way of example, let's take Alabama. Alabama's SOS isn't going to be as strong because the various SEC teams beat up on each other. Yet, everyone accepts that the 2nd or 3rd SEC team that might have 3 or 4 losses is on par with the runner up in the Big 10, Big 12 and Pac 12. That's what I mean when I say I can make the stats say anything I want. You interpret it as gospel rather than really thinking about what goes into the metric.