Originally Posted by Steve Smith
I think it's a myth that the pc socket can handle a higher voltage than the hot shoe. Why should it? It would be designed with the same circuit or a parallel connection.
I think the reality is that some manufacturers are worried that in sliding a charged flash into a hot shoe, the centre pin might make contact with one of the other contacts and cause damage.
The PC sync socket doesn't take higher voltage than the hot shoe. Only newer camera has lower voltage rating for the flash sync circuit and it's for both the PC connector and hot shoe.