How much Patton's fictitious army contributed to D-Day

Are claims about Patton and the ghost army's contribution to D-Day overblown?

Only when they are presented as decisive by themselves; the deception diverted German resources but was one element in a much larger plan.

Patton's notional force helped hold German resources away from Normandy, which made it an important contribution to the invasion. Accounts that treat the deception as the single cause of victory overstate its effect. Fortitude worked as one part of a combined operational system that also relied on naval, air, land, intelligence, and logistics advantages.