I think this is the tasting they speak of https://www.jancisrobinson.com/articles/english-fizz-trumps-...
They're comparing the very lowest end of Champagne with similarly priced English sparkling wines. These aren't bottles people would generally consider good champagne. I'd be curious what'd happen if they repeated this tasting with midrange and high-end bottles, although those don't really exist when it comes to English sparkling wines.
I suspect that the Champagne would win if you blind tasted the very highest end of English sparkling wines with midrange Champagne from Selosse, Collin and Krug. This isn't a fair comparison though, because the fanciest English sparkling wines retail at a fraction of what midrange Champagne goes for.