Yes but the article implies that they somehow made 15B in profit by selling the gold in US and buying an equivalent amount which can’t be the case.

What happened was that

a) they bought the gold long time ago for basically nothing and had it on their books valued at basically nothing

b) they sold it now (in the US) for around $15b and thus for accounting purposes realised a $15b gain

c) they bought it back (in France) for around $15b and will have it on the book now valued at $15b.

The fact that the gold price rose over the course of b) selling and c) buying doesn't matter (despite what the article implies). That the gold price rose between a) the original purchase and now b)c), that's what resulted in the profit.