That’s a fair question regarding clarity — the authors of the study touched on this in the “Strengths and weaknesses of the study” section:

Before we can infer that E-HE vehicles pose a greater risk to pedestrians than ICE vehicles, we must consider whether our study is free from confounding and selection bias. Confounding occurs when the exposure and outcome share a common cause. Confounders in this study would be factors that may both cause a traffic collision and also cause the exposure (use of an E-HE car). Younger, less experienced drivers (ie, ages 16–24) are more likely to be involved in a road traffic collision and are also more likely to own an electric car. Some of the observed increased risk of electric cars may therefore be due to younger drivers preferring electric cars. This would cause positive confounding, meaning that the true relative risk of electric cars is less than we have estimated in our study.

The study is technically looking at the unit of driver and vehicle, rather than only the driver or only the vehicle, so the results could potentially be different if the driver and car are viewed as a unit rather than separate.