There's very little benefit to using Expert Driver Speed on Bulma Bike. When you aren't boosting, it does speed you up considerably, however most of the time you'll be boosting and you only go 2m/s faster with +20 expert driver speed. I don't think that's worth it for a whole passive slot for just +2m/s.

It was the same before the Season 9 speed nerf as well. (23m/s vs 21m/s)