Yes, +50% velocity is quite different from -50% time taken, as you would need to double your DU/frame to travel the same distance in half the time.
There's no deception here. If you have max Run Speed Up, you will move 50% faster than anyone with none. You will reach the opposing spawn point by the time they get 66.7% of the way there. It will take them 50% longer to catch up to where you were at any given time.
Or looking at it in reverse, if you do not have any Run Speed Up, you will move 33.3% slower than those who are capped. For every step you take, they go 50% further. They will spend 33.3 of the time waiting for you to catch up.
Let's say a railroad track is 72 DU long.
Train A is traveling at .96 DU/frame, and Train B is traveling at 1.44 DU/frame.
How many frames does each train need to reach the other end?
If the two trains start from opposite ends, how many frames will it take for them to collide?
How many DU will each train travel in the time it took to collide?
So then, exactly how much "faster" is Train B compared to Train A? 2/3 or 3/2?