The pre-order delivery date will never be ahead of the public release date.
Case in point: iPhone launch date always held at UPS warehouse until the day of delivery/launch day.
My last pre-order thru Apple was spot on - M1 Mini launch day November 19, 2020 = day of delivery.
This current (customized) pre-order for the M1 iMac I have a window of May 21-27 which tells me that May 21 is the public launch day.