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Yes, but what is so exceptional about that variation? It seems quite standard as dialects go. It's not only Switzerland--if I go to deepest Swabia, Bavaria, or Austria, I won't be able to understand the local dialect. Dialect variations are certainly more pronounced in German than those in English throughout the British Isles, probably because the role of dialects was often taken on by vestiginal Gaelic languages, and what we understand as an 'accent' was people trying to speak 'standard' English, albeit with the inevitable lexical variation creeping in. I haven't studied this, though, so that may be bollocks.
Oh, and in bits of Valais, the Schwyzrdütsch/Schweizerdeutsch pronounce 'drei' to rhyme with the English word 'tree'. Madness, I tell you. Ordering three coffees never used to be this hard...