Is this to prevent the Orange man from stealing it? What do they imagine the risk is?

Stated in another article it said the reason is it cannot be used as a bargaining chip during trade disputes. They specifically mentioned it would likely be more difficult to use in emergency situations when located in North America (without mentioning specific reasons).

Well, one of their near neighbouring countries is currently worried about Trump stealing their territory, and he's made threats to annex Canada too, so it's not exactly an unreasonable fear.

Would you put it past Trump to use gold stores as a threat?

Their national color is orange so they should get along with him fine