Bought a mk1 focus Rs new from ford back in the day, my seats were the later type with stitching across, really liked them and don't remember any issues with comfort etc.
As a regular track day goer it was obvious to me the seats were all show and for road use without harnesses but the style of them does suggest harnesses could be used, I was never told by ford not to fit them or that the seat couldn't stand up to a crash if fitted.
Looks a really bad crash and a test for anything used to survive it, what would the injuries have been in a roll situation using seatbelt? Wish the guy driving all the best in his recovery and hope the surgery goes well.