According to the statement, due to chemical treatment for rust protection, rust can not penetrate from surface to bare metal. It doesn't say about protection level or period of time that this treatment protects the frame. It's irrelevant how many Bromptons out there or for how many years. According to this statement rust can not penetrate from surface to bear metal. And it
obviously can . Anyone with rust in the frame or fork can take Brompton to court any day based on this statement, which is probably why they removed it. So yeah, this statement is BS.
And precisely because Brompton frames rust, just like any other steel frame on any other bike of any other producer, users like me are looking for means to protect it from rust.