No Rob, it's not the hay. It's the air. Canadian air is more transparent to hay colour frequencies.
Ps: The X3 sensor does seem to have an affinity for yellows and oranges. It doesn't do them accurately, but it can be attractive. I saw this last year when testing the SD1 as well.
Canadian air and water are surely the culprits.
On the other hand, Sigma designers may have been affected by the yellows and oranges in the scotch.