I have one question about LTC4418

Looking at P12 of the LTC4418 datasheet, we have the following description.

「Note that input supply voltages denoted by “SYS” are not hot-swappable, all other input supplies are hot-swappable.」

Is this SYS a system power supply and recognition?

If you are supplying power from an AC battery, USB, battery, you can read it if you can hot plug in and out.

I understand that it cannot guarantee a hotline under other input conditions?