Golds, and I think Silvers, can board whenever they want. But as pointed out already, it depends on the airport and the person operating the gate e.g. at AMS, if they announce they are boarding strictly by seat row number, they mean it. You can be Gold, Black, or any hue between, but you need to wait your turn.

Having said that, invariably the front lockers are full by the time you get on...