I inferred that, since he couldn't be talking about an effect at constant velocity, that this effect would be an extra mysterious hazard of extreme acceleration

I inferred that, since he couldn't be talking about an effect at constant velocity, that this effect would be an extra mysterious hazard of extreme acceleration - beyond the mundane hazard of being crushed into a damp spot on the bulkhead. Perhaps related to the tidal deformation one would experience falling into a black hole. The consensus here is he just blew it - nothing more to be concerned with.