Our own e-bike ranking surprised me: 17 of the top 20 are brands that mostly sell online. And when I dug in, it wasn't that bike-shop bikes get worse reviews, but they just barely get reviewed.
Yes, that's the split we see. Set 2 is always more negative, so the interesting part isn't how negative it is, it's what the complaints are about. That varies a lot between categories.
Probably part of it. A lot of reviewers get their units for free and it's easier to be happy with something you didn't pay for. We can't tell which reviews were sponsored, so we can't measure that directly.