"Force Speed" is completely dependent on script requirements, not force ability.

For example, Obi-Wan can use it freely in the beginning of Phantom Menace to escape the droids on the Trade Federation ship, but during the fight with Maul at the end of the movie he is unable to use it because the script says he must be separated from Qui-Gon.

Kind of like in Attack of the Clones when Anakin says to shoot down Dooku, but they can't because they're out of rockets. The 12 or so laser guns on the ship had been disabled by the script at that point.