You are correct! The main difference is that it's boost only applies to the legs, although keep in mind when you attack that you slow down to your normal speed rather than moving at x2 the speed.
Now, put these on *Tosses LW* and have a month long training montage!
( Katai Omori ) - Leg Weights
Type: Weapon/Supplementary
Rank: A
Range: Short
Chakra: 30
Damage: N/A (+20 to Kicks, 2x Running Speed)
Description: The Leg Weights used for Special Taijutsu Training with Added Weights are made through the application of a sealing formula to ordinary leg weights. The sealing formula is used to, through the use of chakra, increase the weight of the leg weights to the desired level. The seal can't be applied to anything other than the leg weights and its use is restricted to its original purpose. One can remove the leg weights but the sealing technique in them stays active indefinitely and can't be released. Additionally, the Leg Weights and their unique seal calibration makes them only usable by the ninja to whom they belong. They can't be sealed or stolen.