When I take my bike to school, there are those "School Crossing Guards." One of them guards a 2 line drive in.
This man uses his STOP sign on pedestrians. Here I am cycling, this guy holds his STOP sign up high so I am like "ok, I can go right across at full speed without breaking or slowing down." turns out no, what he actually meant was that all pedestrians (up to 5 people sometimes) should stop and the car should drive. 50% of the time in the car is a friend of his who stops in the middle of the crosswalk and starts chatting. I look and this and go like "my classes start in 10 minutes, so I am crossing." They both, he and his friend look at me like I am some self harm guy jumping under a car, and start shouting at me like why I am going when the STOP sign is up.
Tldr: When you ride on a sidewalk, the risk of a driver hitting you at a driveway or intersection goes up substantially. That outweighs most of the other risks of being on the road itself in those studies.
Although it's also worth pointing out that context and road design matter too. Speeds, the number of trees and shrubs by the sidewalk, and urban streets vs suburban stroads matters a lot.
There's a reason that protected bike lanes aren't just a sidewalk.
bicilists drive way faster on the roads, so this metric should be deaths per km/h. And there are a few more stistical biases that might be at play here.