Can someone clarify the response to the OP's question about having one PSU for the motherboard and the Server PSU dedicated to PCIE adapters for the cards?

I read the reply where someone said they turn on the server pSU 1 second before the main power, but I was wondering if there were opinions on this. I have read other people online say not to do that, but they didn't display a reason why/how it is dangerous.

Thanks