Was the sign official? I would have simply waited for an opportune time and either removed it, or scribbled something more appropriate over it

What is the logic behind this? If I want to switch trains to go to an adjacent terminal pod, I have to go through security again because they don't want to re-screen int'l arrivals? Screw that! Once I'm airside, I should be able to transfer to the next terminal pod over without being re-screened.