I understand that seabios parses the grub config and attempts to create kexec commands to launch the kernel. This works great on PureOS but fails with the Arch boot iso. I can parse my own kexec commands and get the kernel to boot but the boot partition remains mounted in seabios and unavailable to the arch kernel. I have a fourm on arch forums as well but have not gotten a response.
Arch forum link with exact error messages
https://bbs.archlinux.org/viewtopic.php?id=271070