That's not how the math works out, it isn't linear. The distance it takes to stop anything is dominated by a term quadratic in the velocity. Thus the average safe traffic density decreases with the velocity like v^-2. Since the throughput will just be the velocity times the traffic density, throughput roughly decreases proportional to 1/v. (In the zero velocity limit, physical size terms would dominate, so you don't get infinite throughput.)

https://www.omnicalculator.com/physics/stopping-distance

So if you do the math, bikes take up less time-space, or said better: achieve higher throughput. They are multiple times more dense at their travelling speeds. The only real way out of this would be to travel at unsafe distances.