A matter of logic

The other day I was passing the ambulance station in Llandod when an NHS vehicle reversed slowly into the road. As it moved an annoying voice, in English, advised that it was indeed going backwards and it would be best if you didn’t lay down in the road and allow it to pass over you. These were not the exact words but it doesn’t matter – you get my drift. This kind of tosh has ceased to be funny but what happened next restored my faith in the boundless comic creativity of officialdom. While the vehicle was still moving backwards they repeated the warning in Welsh! I don’t speak Welsh and so I thanked my lucky stars that I happened to have arrived while the vehicle was giving me this important message in English.
Now here is a little exercise in elementary logic.
All Welshmen speak English.
Some Welshmen speak Welsh.
It follows from those two premises that if a warning has to be given in a language then it should be given in English alone since all Welsh speakers understand it whereas not all English speakers understand Welsh.
If there is any argument at all for a warning in an additional language then I regret to point out that Polish would have a much better claim than Welsh.