On sprint tracks, if the start line is behind the starting position, timer during the race starts immediately when the race is started on GO!. In that case, in Time Trial, timer starts immediately when the track is loaded as in TT you immediately have control over your car. Repositioning the car in sprint races in time-trial resets the car to the starting position, as on regular tracks. But when the start-line is behind the player, meaning the starting position is already ahead of 0 distance POS Nodes, resetting the car doesn't stop the time trial time from running. In that case, game should detect that the start-finish is behind, the player has repo'd and it should reset the timer the moment when car is beginning to appear on the start-finish line, just as on restart of the entire track.
My understanding is that the game doesn't recognize the repo button as the reset of the time and the start of another one, but rather it detects when the car is in the "0" zone of POS Nodes (in the case of a sprint track) and that's when it stops the previous try and prepares for another one, zeroing the time trial time and waits when the player crosses the start line. If there is no such "0" POS Node zone where the car is positioned after a repo in TT, timer goes on and game thinks you are still running the first time trial run.
I'm not sure if that's the case on regular tracks as all of which I played are correctly placing the car behind the start-finish line on repo and time is reset when your car is starting to be placed in the TT repo place.
Start and finish, POS Nodes, there is no "0" zone at the start and the start line is behind the TT repo place/race start place, there is "0" zone after the finish. Timer doesn't reset when you repo. Track: Phantasmabyssal Turbulance
Repo correctly resets the time if there is a "0" zone where car is placed when resetting a TT run. Track: zzz-Acceleration-Lab