How? You can buy the same wine from the same year in both UK and France. It is the SAME - apart from the price of course.
Or are you talking about different years? In which case it’s probably down to the wine buyers thinking they can pass on a poorer, cheaper vintage. Nothing to do with the French (unless the wine buyer is French of course).
And I have been drinking wine in both countries for many years, and your idea is nonesense. As are your viewson what is decent wine.
And your French guy knew what AOC meant, so not such a stupid idea.