Unintended Cruise Control Acceleration?

Yes. This is related to the dynamic/adaptive cruise control and it is operating correctly.

Watch the MID. It will tell you what speed you're setting it to. Lifting and holding will incrementally increase the speed (originally, it's 1mph per tap and 5mph when you hold... I think that was changed to 1mph even when holding because of the scenario you described and people freaking out about it accelerating to a higher speed).

DRCC will indicate the set speed in the MID. You tell it what speed you want and it'll get there (using the radar as a guidance whether there is a car or not in front of you).

 

It depends on whether you're in DRCC mode or regular CC mode. If you went into regular CC mode on the Gen 4/Prime or Gen 3 with DRCC, it'll operate like the old CC where it will increase/decrease speed until you release the stalk. But DRCC works differently since you can see the set speed on the MID and thus you can choose the set speed visually and then the car will do its thing. This is because you can change the set speed to adjust to the current environment (i.e. traffic or construction) without cancelling CC. (e.g you set the speed at 70mph, you enter a construction zone following someone ahead so you both slow down to 40mph but the DRCC is still set at 70mph. For me, sometimes I might drop the set speed to 50mph just so I don't get a sudden acceleration if the guy in front changes lanes but it doesn't change the fact I'm still doing 40mph following the guy ahead).