If you overload any ONE output then you are overloading the entire SMPS
circuit. Standard SMPS operation dictates that each and every winding
output must remain below load. Some SMPS need a load on every output
as well.

SMPS supplies that are showing the MAXIMUM current output. Normally
you cannot simply load the outputs all at once a turn on at maximum
load as this is not how it would operate in a normal circuit.