> Covariates. We control for covariates that are likely associated with both psychological distress and marital strain including respondent age, education, and employment status (Mirowsky & Ross, 2003), spouse health status (Kiecolt-Glaser & Wilson, 2017), relationship duration (Proulx et al., 2007), and children in household (Mirowsky & Schieman, 2008).

So at least they attempted to account for obvious covariates.

They didn’t make this claim.

> "well I bet they didn't control for obvious thing X"

Is a close paraphrase of

> if they did not correctly control for kids, it is useless

The comment seems to be intended as a dismissal while calling itself out as uninformed (“cannot be accessed without payment” suggests it wasn’t accessed).

TBH I am not familiar with the the way data is presented in this last link, and likely biased toward my own expectations, but my uneducated read of table 2 says that children, education, being a woman, and employment status are the largest contributors to the distress.