It is a matter of practical fact that only a small proportion of the Andriod-using public chooses to use the software of their choice by sideloading. Mentioning sideloading in this context shouldn't be interpreted as an attack upon or a dispargement of the practice of sideloading. I, as an Android user, am happy to learn that the (main?) vector of attack happens to be sideloading. (if true) This informs the broader conversation and helps individual Android users gague the likelihood of whether they have may have been directly affected.