An important caveat for Psychology studies is to ask, "If the participants are told exactly what is being measured, do the results stay the same?" If the answer is "No" you should question the validity of the study.

Here for example, if you tell people that "intellectual humility; taking the perspective of others; recognising uncertainty; and having the capacity to search for a compromise." all lead to "emotional wellbeing, and relationship satisfaction" just prior to taking the test, would that effect size be similar to intentionally omitting that information and having people journal for four weeks?

As far as I can tell there was no informed control cohort in this study.