No EG-S focusing screens 
Are you sure the standard 1DX focus screen isn't equivelent to an EG-S screen?
Yes, its laser etched.
How is the S - super precision matte made? Isn't it also a laser etched matte?
My point it the standard EC-CV is a new focus screen with this camera. You're already complaining that the software doesn't support EC-S focus screens, maybe that is because the NEW EC-CV screen makes them unnecessary.
Doesn't matter if that's true or not, the Nikon fan bois will grab onto this for years, 'the Canon 1DX doesn't support the EC-S focus screen', 'but, the EC-CV made the EC-S obsolete', 'doesn't matter Canon messed up again, they should have added support for the EC-S screen, my Nikon camera supports every focus screen made since 1937'