> Note that you can build seabios as CSM for tianocore already.
These are the opposites: SeaBIOS is CSM ON (emulates Leagcy BIOS), while Tiano Core supposed to be CSM OFF (UEFI), Thus, SeaBIOS and Tiano Core exclude each other (should not be used together -> wrong architecture).
> What is the point? You can just run tianocore as coreboot playload.
The point is to make minimal Tiano Core (minimum for making FAT32 partition/file system on HDD/SDD to create /boot/EFI/ directory, in other words minimal UEFI compliant BIOS), Tiano Core as such is good to be used/run for/on x86 architecture ONLY (and side effect is the extended time for booting, since all these DXE drivers must be installed, which will be later mostly replaced/run over with OS drivers, except run time services).
As such, Minimal Tiano Core (minimal UEFI compliant BIOS) could be used on ARM architectures too, thus making ARM HW platforms also compatible/lookalike as x86 UEFI compliant BIOS.
In nutshell, then you can build PC/Laptop with ARM CPU/SoC HW platform, having coreboot + minimal Tiano Core + WIN 10 Boot Loader + WIN10 on it (since WIN10 BL does see UEFI compliance, not knowing what is really under the hood). ;-)