From the study:

Although, our findings suggest that e-scooterists may be safer than e-cyclists in urban environments, we only considered crashes involving injured riders using a shared system in a few European city centers in one year. We also assumed that underreporting—an important and well-documented issue especially for micromobility—affects e-scootering and e-cycling equally. Furthermore, the relatively small number of e-cyclist injuries in some of the studied cities (and the absence of reported e-bicycle injuries in two cities) highlights the limitation of the dataset and introduces a degree of uncertainty into the injury rate comparisons. We did not consider whether post-crash consequences and injuries may be more severe on an e-bicycle (where the rider seats higher and dismounting may be harder) than on an e-scooter. It is important to acknowledge that injury data were self-reported by users. However, in the context of this study, where users had no clear incentive to misrepresent injuries, we believe the potential for misreporting is limited. Finally, we assumed the two customer populations to be equivalent. Therefore, while our study is enough to challenge the current scientific literature portraying e-scootering as riskier than cycling, our study does not provide conclusive evidence that one vehicle is safer than the other.