Sorry mate, It's so confusing to read your response because you go off on multiple tangents.
1. Yes 125 enduro bikes can be A1 legal in Europe, EEA and the UK.
2. If you don't consider a 125 enduro bike a proper enduro bike, that's fine. I've seen enough people ripping on 125's to know they are more than capable.
3. Welsh 2 day enduro: I haven't looked into the rules but i'm sure if someone wants to make it work they will. Stark seems to have done fine against ICE bikes in other enduro event's
In trying to break down what you're saying, my understanding is that you are trying to say that the Stark isn't a proper enduro bike as it can't finish an enduro event and it won't be legally allowed to be registered as A1?
Part 1 of that is subjective and part 2 of that looks objectively wrong as they are being classified under A1 in the EU, regardless of how crazy that is.