The video doesn’t show him “striding to the door”. It shows a taxi pull up quickly, the passenger door opening before it stops, and a guy bails out and rushes the front door. I doubt the cop in the booth by the door knew he was a spy. He actually looked like he was someone you would stop anyway, like a suicide bomber or someone maybe not authorized.
Maybe you’re right. I notice the cop isn’t trying to hurt him, only restrain him. It isn’t a beat down.
I’m leaning toward what you say. Cop doing his job.