Rehearsal for security theatre?

At Changi, they check everyone's bags and boarding passes through an x-ray machine before you go to immigration, but the check feels a bit suspect because there's none of the expected take-your-laptop-out rigmarole that you get when you are checked again at the boarding gate before you get on the plane.

It doesn't feel that efficient, which is surprising for Singapore. Unless the dread hand of the economist-king is optimising for maximum-bottles-of-water-purchased-from-the-duty-free-shops. (You can't take more than 100 ml through the first checkpoint, but if you buy notionally terrorist-free water after that, you still can't take that through the second checkpoint. It's almost as if it were some immense boondoggle, whatever one of those is.)

However today, with twenty people in front of me at the first checkpoint, milling about and forming an untidy line, an angry security guy told us to not waste time, and sent me away from the line for the x-ray machine, and straight to passport control.

Which suggests that they're only going to x-ray bags if they're not too busy. What does that imply?

Unilateral decision making by one guy to shoo us away from his x-ray machine because he's in a grump today? I don't think that airport security is meant to be defined by the mutable emotions of random employees.

Security checks are not worthwhile when people are busy? That doesn't seem a very rational approach, unless we assume terrorists enjoy blowing up empty buildings more than full ones. (Actually, there is the argument that the IRA did better when they concentrated on blowing up buildings and _not_ people, but you don't hear much about the Fenian Brotherhood in south-east Asia. It's not like the Malaysians have been busy occupying Ulster, after all. I doubt this is the right venue for that debate, but since the people you do hear about over here still seem focussed on generating high death tolls, only guarding the place during off-peak hours doesn't sound such a sensible approach.)

Or could it just be that the first check is a combination of make-work and pretending you're doing something significant, when you've got a security cordon a few minutes later anyway that's meant to accomplish the same thing?

Or perhaps Changi Airport's bosses really, really enjoy x-raying bags, bags with laptops in them, bags without laptops in them, bags made from laptops, bags without end, and it just so happens that the occasional grumpy employee in the organisation is so allergic to people that he just panics when he sees a crowd, and shoos them all away.
When you've removed the impossible, what's left, no matter how improbable is the solution.