I think thats true. I’ve got a training partner who is a bobsled driver and he made us modify the car pushes to make them a little more specific. We pushed hard for 10m,then the driver put it in drive and it made it a little easier, then the driver starts to accelerate away and we had to keep up with the car. According to him, this was the closest thing to bobsled.
As for the sled weights, I think its ok to go over 10% bodyweight. A 20lb sled for me is pretty light, I’d have no problems pulling a 50lb sled.