On topic, I personally always thought it was telling me I had to slow down, thought I kind of understood why. Basically it's because the max speed decreases based on how close you are to your target in SC (you can watch it drop even though you aren't doing that yourself). What happens is you end up not being able to slow down because your ship has a limit on how fast it can decelerate, adding in the fact that the ship will reduce you max speed the closer you get... you end up in a situation where you can't decelerate faster than your max speed drop due to the proximity of your target. In this case, it is telling me that I am going too fast.
My previous post I explained that if you wait until "6" seconds and go to 75% throttle you will coast in perfectly, this is because it hits an equilibrium where you are slowing down at the same rate your max speed reduces. Think of it like belly surfing in an ocean with your max speed being the wave.
Not sure if that makes any sense.