I would need to do a bit of digging to be sure of this... I read somewhere that the old vacuum tube devices are not particularly susceptible to emp nor were old (real metal ) non electronic cars. This might be simply a matter of overbuilding. Today's electronics cannot handle the voltage/...
It gets into definitions... atoms never stop moving except at absolute zero... but an object can not, on a linear path, take a reciprocal course without first stopping. The piston might rock and/or pivot in the cylinder but the implied relevant motion is along the cylinder axis. It's a bar...