It's low-voltage protection, not low-power protection.
The low voltage protection will engage when the voltage at the B+/ground is drawn too low. It's common for this to happen when a power supply with insufficient current capacity dips in voltage as the rail caps try to charge. When this happens, the amp will pulse on until the caps charge and the inrush current is low enough for the voltage to remain above the low-voltage threshold.
Besides normal inrush current, excessive current draw from some fault can cause the amp to draw the power supply voltage down and engage the low voltage protection.
There are, however, other protection circuits that can shut down the amp.