First what is your definition of full utilization and what aspect of the system are you talking about being fully utilized.
Second unequal headways on crowded lines cause problems, althought I will never prove that to your satisfaction.
Third look at a busy highway, when there is an entrance without adding a lane traffic slows down.
Fourth how do YOU know otherwise. You load your question by assuming 75%. You dismiss all my methodology without saying how it is wrong.
You accept no questions or critiscisms of you methodology. You evidence is 40 YO timetables which were from the days of the ABD.
You make demands for service that need alomst twice the level of staffing with no way to pay for it.