Well, it could have been the brake assist simply because of the pedal effect you described above, although it is hard to tell.

Was your brake forceful enough to the point you felt the ABS kick in? Did the tires lock and screech?

 

^^^No, not even close to an emergency stop. That's what was kind of strange. I could of cruised in for a normal slow down but all of a sudden the brake pressure stiffened up and I went from ~40 to nada as if I was exerting all the pressure I could on the brake pedal.

 

Not sure if this is what happened in your case but I have experienced similar behavior with the Preview Braking. The ICC sensor is good for more than cruise control and is a great safety addition to the vehicle. This feature is often overlooked in the tech package. 8 car lengths is certainly within the sensor's distance. I have brake assist in my '02 Maxima so I know how that feels.

 

Is this something you would be able to reproduce for the dealer's service techs? If so I would consider having them check it out. I say this because I have occasionally had to manually do something like what you describe (braking normally and then suddenly hitting the brakes really hard - usually due to the guy in front of me doing the same)... and I swear every time I've had a big-old Texas pickup truck millimeters from busting up my tail lights. I'm just saying watch out for the guy behind you cuz his brakes probably aren't as good as yours and he won't have magical brake pixies that help him stop short suddenly when yours do.