The spiral hook shown on the link above is the one which came with my N50. It appears to me that Hobart fairly recently replaced the antique C-hook by the spiral new one.
If we refer to the Hobart denomination : 'E' = C-shaped, and 'ED' = spiral. So, if you bought a 'ED' hook, then your local distributor should have provided the spiral new model, but maybe he preferred to sell an old C-shaped remaining in his stock.
By the way, I already bought another N50 hook from Globe, and they provided me the spiral one, even if the photo on their website is not up to date (the C-shaped is supposed to be discontinued).