Both of those examples are non-continuous loads.
If you had the six circuits all supplying electric heat circuits it would be unusual for all six circuits to have each of their zones all needing heat at the same time.
I take, as I am sure you do many current readings.
It is unusual for many circuits to be at 60% load in a dwelling unit.
Proof of this is the fact you may have 500 amps worth of breakers in a 200 amp panel.
Anything is possible but we regularly assume certain loading characteristics, most of Article 220 is based on assumptions.
