Probably would be more accurate to say that TianoCore now supports the board. UEFI could be ported to more systems, but there's little incentive. Also, the main power of UEFI is the ability for an OS to get an early framebuffer and nice interface to USB/PCI/etc. without knowing the low-level details of the system you're booting, and that's a lot of work, especially in the embedded ecosystem where SoC vendors just rearrange memory layout and blocks between chip revisions (hey, we'll just update the Linux driver with the latest mappings, that's fine, right?)