I used to work for TSA and I can assure you a laptop IED is insanely easy to spot on an x-ray. It’s even obvious when you have removed a simple component. But yes, there’s a lot of arbitrary rules. For instance you can bring sharpened ice skates but not a 1in swiss army knife?? WTF.
Fun fact, you want to bring water on the plane? Just freeze a couple bottles solid and drink any melt right before going through TSA. Ice isn’t liquid. Or if you have a medical reason you can bring liquid over 3.4oz, within reason, and TSA can’t ask you specifically what your medical condition is. They just need to preform chemical analysis on the liquid to prove its not something like nitro, and you’re good to go.