Deploy-OSDCloud always wipes the target disk and creates a fixed 500 MB EFI system partition. If we prepare the disk first with New-OSDisk -SizeSystemGpt 2000MB, Deploy-OSDCloud wipes it again and goes back to 500 MB. Right now there is no supported way to deploy with a bigger EFI partition through OSDeploy.
like; Deploy-OSDCloud -CLI -Force -SizeSystemGpt 2000MB