TPS2411: when MOSFET is short, Fault is inserted during startup.

Hi

This is our application :

When we short ORing MOSFET Drain and source by a jumper(equivalent to short pin A and pin C) . We find that gate cannot high and FLTB pin goes low during startup . We understand that there should be no gate given out but we don’t understand why FLTB goes low which means fault.

1. What does “ON” mean in the following block diagram ?

2. Why FLTB goes low when we short ORING FET drain-source ? Please try to explain base on the block diagram.