How that? Switching losses are roughly proporional to switched voltage, current and rise/fall time. So they are proportional to load current. Similarly diode recovery losses are proportional to √Id, if MOSFET diode operation is involved or for an IGBT inverter.
A constant switching loss share is caused by the magnetizing current of output transformers or inductors and by the MOSFET capacitances. Additional constant losses are generated by the control circuit.