Sprint moved onto the stick you steer with
For twenty-five years sprinting meant tapping Cross or A. In VI it is a click of the left stick — the same stick pointing you down the street. Pressing down on a stick you are holding off-centre moves it. Push the stick, hold it, then click.
Confirmed by creators who played the preview build: sprint is a stick click by default, not repeated taps of Cross/A.
The page measures how far your heading moves at the moment the click lands.
Why degrees. The game is not out and a number in game terms would be invented. Degrees of heading change is a property of your hand on your controller. As plain trigonometry, 10° of error puts you 1.8 m off line over ten metres of running, whatever Rockstar's movement code turns out to do.