My guide was very explicit to hold off on payment until we knew when the truck was going to make it to the service center. I was told about 4 weeks (via rail) from Normal to South SF. I locked last Friday, expecting shipment this week.
FYI Rivian is not a “preferred“ OEM/dealer for BofA, so if you’re funding through them, you get an extra couple of steps. Best rate I have available though so it’s worth it.