They did from time to time encounter many problems sourcing suitable walnut for the manufacture of their stocks and the diversity of walnut stocks quality etc is quite surprising, I have seen quite a few different types, indeed my own Mk1s vary greatly! At one time, the stocks were outsourced to Italy due to problems in supply. (the one piece ones)
So no!- frankly I wouldn't be at all surprised if that was the case but it's more likely that a lighter or different type of walnut has been used for the forend 'forks' to that used for the actual Butt section - now that I have seen myself!

Not an expert - it's just what I have seen, read and heard (from different sources) over the years!

ASM