I've seen pro-marriage people on PPD quote marriage surveys where men report higher levels of happiness and satisfaction, whereas red pillers will say that most men in marriage are mistreated beta buxxers. What could be the confounding variable causing this discrepancy between surveys and what red pillers are seeing with their own eyes?

I think it is the fact that within relationships that are clearly based on beta buxxing, you have an extended period in the beginning and middle of the relationship where the men bury their heads in the sand about how they are being used. This period could last for years and you will be amazed the lengths to which men will rationalize their beta buxxing during this time.

Only at the tail end of the relationship when everything is fizzling out, are the beta buxxers willing to be honest about the fact that they were being used all along by their wives and girlfriends. We would need a decades-long longitudinal study about marriage satisfaction to get to the bottom of this issue, but most studies measure satisfaction at one point in time and that skews the results.