It probably does happen more with any "self driving" car or anybody who uses smart cruise control, because the driver may not be using the pedals at all before the incident.

a really good point I'd never considered when thinking about accidents like these.

Intuitively it makes sense. If my heel remains planted in front of the accelerator pedal even if I'm not pressing it, I still have a frame of reference to know where the brake pedal is. If I'm using all the fancy assisted driving stuff on a long stretch I may relax a bit and pull my foot back, but that does mean if I need to slam on the brakes my reaction time will be worse, and I run the risk of hitting the wrong pedal since I don't have that anchor point anymore.

good thing to be mindful of when using cruise control of any type, newfangled or old school.