Why Polish forces did not receive a separate D-Day beach

What would have happened if Polish forces had received their own D-Day beachhead?

Poland lacked a large separate amphibious force for another beach, while its strong armoured and motorized formations were better employed after the landing.

A separate Polish beachhead would have required enough assault troops to justify another landing sector. Polish formations in Britain were especially valuable as armoured and motorized forces, which were better committed after the beachhead existed. They could then operate with the wider Commonwealth force. The decision concerned force composition and timing, not the fighting quality of Polish personnel.