That article provides a link to this fascinating pre-print:
https://www.biorxiv.org/content/10.1101/2021.07.29.454333v1
"We conclude that memory antibodies selected over time by natural infection have greater potency and breadth than antibodies elicited by vaccination. These results suggest that boosting vaccinated individuals with currently available mRNA vaccines would produce a quantitative increase in plasma neutralizing activity but not the qualitative advantage against variants obtained by vaccinating convalescent individuals."
(However, quite the non-sequitur in the conclusion as there is nothing which suggests any benefit gained from vaccinating convalescent individuals.)