Are the peak current draw values reported by the motor suppliers or calculated by other means additive? Also, is this on the power supply side of the ECS or on the motor side of the ECS? What I mean is if I have 4 motors and peak current draw is determined to be 20 Amps does that mean an XT-60 connector is not sufficient, as 4 time 20 is 80 Amps?
If I understand your question, current is additive in a parallel circuit as multirotor motors. The manufacturer lists the nominal peak current draw for the tested motor.
But you might still be ok in the scenario described. See: https://www.youtube.com/watch?v=qEdysiZAYZ4
Keep in mind the total current must also take into account contributions from the demands of the flight controller, receiver, payload (eg, gimbals, cameras, sensors) - unless separate batteries are used (which I do).