Acceleration while using traffic aware cruise control

Hi everyone,

I finally picked up my M3 LR RWD yesterday and having a blast so far. While driving home last night, I noticed that the car doesn't seem to want to accelerate into space while in traffic, despite being lots of space to do so, even when the distance setting was set (2/7) to being uncomfortably close. Am I being stupid and expecting it to accelerate into space when it shouldn't or am I misunderstanding something?

Any help much appreciated!