another switchmode trick called bootstrapping is when you run the smps off the output, usually 5v switched down from 12-24. in order to get the smps to start up, it has the top gate on in shutdown or power down. Once enough voltage flows to bring the part out of undervoltage lockout it starts to PWM normally.
but bootstrapping to prevent hot switching? sounds like a hotswap configuration that also allows the output to charge a little, but that is the definition of hot switching so it seems unlikey as a prevention method.
what's the ckt? got a link or datasheet?