I can’t see any cord visable on that tyre and had a magnifing glass on it and a small slit in the tread of a tyre is generally not a cause for immediate failure during an MOT 🤔
MOT’s  don’t specifically address the issue of outdated sealant, just as spare wheels are not covered in a test🤔
Makes me wonder, whether your wiper blades had cut’s slits or were worn!
Anyway, as suggested, I would get on the blower to Motability and query whats going on, as your picking up your new car tomorrow.