Sounds like the pre-production board is for people who can't wait until a production board with mainline Linux support is available:

> The pre-production developer board is fitted with NXP LX2160A pre-production silicon which explains some of the limitations. [...] software features will be limited with the lack of SBSA compliance, UEFI and mainline Linux support. It will support Linux 4.14.x only.

BTW, would be nice if the production board had Coreboot support, whether or not it has UEFI by default.