I'm sorry, but no. Yes, important all going same speed, but all else equal slower = safer. more time to react to unexpected events. better traction to road. less energy in a crash.
Basically, you set the speed limit at the speed most of those drivers are already naturally driving at, so that the people who do mind the speed limit will travel at the same speed of travel as everyone else.
And then, of course, obviously there will be outliers.