The real question is: What happens the unerring linuxbios user only specificies only CONFIG_CONSOLE_VGA, and still expects it to work with a vga rom. But this is a purely an issue of bad former practice and bad documentation.
Both options should be specified if both are needed.
I think it is pretty clearly stated here:
http://linuxbios.org/VGA_support
Also this might help some:
http://www.linuxbios.org/data/vgabios/
Thanks - Joe