2023 MY is not scheduled to start until the second week in May AND that has always been a tentative date. IMO it could easily get pushed into the 3rd or 4th week in May. Only GM knows for sure, but every year since the beginning of the C8 they have extended the model year.
The situation may have changed in the past 3 months but sometime around the end of last year there was some parts supplier delivery scheduling info that suggested Z06 cars would start going down the line in April.