I'm pretty sure that's not quite right.
What you've said is that everyone runs at the same speed. So if it's set to 75 threshold, then a 60 speed player would run at 75 speed, and so would a 40 speed player, and so would a 74 speed player...
My interpretation of it is that it's a limiter. So basically, a threshold of 0 means that there is big difference between a 95 speed player and an 80 speed player.
If you set it higher, say at 50, then every players speed is condensed and is less different from each others. So the 95 speed player wont get away from the 80 speed player as much as he did when the threshold was at 0, because the maximum speed has been lowered.
Probably easier to think of it as when threshold = 0, maximum speed is at 100, so a 90 speed player would run at 90% max speed which is 90, 80 speed player at 80% speed which is 80, etc.
When threshold = 50, the maximum speed is 50, so the 90 speed player runs at 90% of 50 which is 45, and the 80 speed player runs at 80% of 50 which is 40.
There's only a difference of 5 'speeds' with the threshold at 50, whereas there is a difference of 10 'speeds' at threshold 0.