Really naive question about the observer effect in QM

[barbos]

That's not quantum mechanical measurement, that can be called "determination"

They're preparing a particle in a superposed state and seeing what detector it shows up in. How do you figure that isn't a quantum mechanical measurement?

They are not measuring that particle, they are using that particle to "measure" the bomb.

Bomb is a macroscopic system and you are not measuring its quantum state here, merely macroscopic shape.
Simpler variant of that experiment would be determining the shape of some perfectly reflecting figurine using interferometer.

Macroscopic systems are made of microscopic systems. Do you know of any theoretical reason for why you can measure a septillion-atom object without interacting with any of those atoms, but you can't measure a one-atom object without interacting with that atom?

What they perform on a bomb is not a measurement. Result of the measurement must be certain quantum state.