That is what is going to make this coin worth something in the future, but actual and nominal weight difference isn't all the rare in coin collecting. It's just rare to see it at such a high degree like being out by 1/2 ounce.
I'm just surprise someone hasn't pulled their head out of their collective butts at
RCM and figured out that this coin should be a 2 Oz coin with 1/2 ounce pieces, this would have been easy to make there "Size" requirement as so they claim the reason for the screw up. Regardless I still think its a unique coin and I will enjoy in my collection for years to come.
Beercules!