Earlier quoted context omitted.
From the full press release: "In 2025 and at the start of 2026, while the volume of gold reserves remained unchanged, the Banque de France had to align a residual portion (5%) with technical guidelines, resulting in a significant realised currency gain. This exceptional foreign exchange income totalled EUR 11 billion for 2025." -- the keyword here likely being "realized"
Is the logic that it's "unrealised" while the gold is stored in the US but becomes "realised" once it is stored in Paris? Why?
They opted to do so because it's just more efficient. It takes a lot of efforts to physically move 129 tonnes of gold after all. And as a side effect of this relocation project, they ended up recording a capital gain. It's nothing-burger.