It is analogous to discrete vs continuous color spectrum. Discrete spectrum clearly separates all colors, whereas continuous spectrum has gradual transition.

My simplistic understanding is that people who dont like uncertainty tend to remember concepts as discrete as possible to avoid mixing different concepts. This helps them in reducing memory errors in distinguishing different concepts. However, this also reduces their ability to generalize, meaning they fail to see similarities among different concepts.

The study doesn't establish any causality. So, it is unclear whether how you remember information determines a dislike for uncertainty or vice versa.