That particular caveat is actually mentioned in the paper: With the self-report, survey method there is often a risk of selective recollection of data as well

That particular caveat is actually mentioned in the paper: With the self-report, survey method there is often a risk of selective recollection of data as well as potential over- or under-reporting. However, there are numerous published, peer reviewed articles in highly reputable journals that use a self-report method, including those that use data sets which rely heavily on survey data (e.g., Der, Batty, & Deary, 2009; Wraw et al., 2015; Wrulich et al., 2013). Additionally, empirical research has confirmed that self-reported health ratings are reliable and valid measures of health (Haapanen, Miilunpalo, Pasanen, Oja, & Vuori, 1997; Liang, 1986).