Yeah, its always been the owners responsibility to keep their car up to WOF standards, and the police issue many tickets to cars with blad tyres while having a wof etc
In reality the only people who would be let off will be girls, and middle aged ladies as they will be presumed to not have known.
If you are a young guy, or a man who shows any remote knowledge of a car, you will be considered guilty on the spot for neglect, regardless of whether you knew or not.
2 sets of rules, depending on your sex (and attitude)