I had a look at your file, something that's important to consider is that KUKA|prc provides an "optimal" simulation and does not simulate the motion blending and possible performance challenges of your robot controller.
In your file, you have got very closely-packed positions that are connected via PTP movements. It might just be, that the robot never even reaches the 100% speed due to point density - that would explain why you don't see a significant change in speed.
If you are worried about the robot ignoring the speed settings for some reason, try some much wider spaced points and see if it improves!
Hope that helps!