A bidirectional pin in output mode could short out your power supply. (Example: if you connect such a pin directly to the positive supply and then the pin tries to output low.)
Only power supplies should have power output. Bidirectional is reserved for pins that can be either input pins or output pins in push pull mode
Have a look at this explanation of what pin types mean: Electrical type of schematic symbol pins (KiCad 4 and KiCad 5)