Did you read the article at all? Or just the title? The article is about bringing gold back to France by selling US bars and buying new bars in Europe. The alternative would be melting the bars down and recasting them to the new standard.
The capital gain is just a by-product, standard financial stuff, but apparently broke HN readers brains.
I did read the article, thanks for asking.
Sounds like you agree with me, France has the same amount of wealth in gold that they had last week.
I don't care about that. That's not what the article is about.