I have checked some Any% and 100% speedruns of Grand Theft Auto San Andreas and it appears that everyone blows up the Picador on the mission Ryder.
Take for example faulux's 2nd place for Any%:
Why this is done? Does this reduces the time of any part of the game?
Best Answer
This video shows it pretty good:
At some point during that mission, a cut scene plays. If you don't blow up the car, you can't skip that scene and you need to wait for it to play fully. But if you blew up the car, you are able to skip that cutscene which saves enough time to be worth it.
This works, because after failing any mission you are able to skip the cutscenes in that mission, so you don't have to watch cutscenes multiple times.
Credit @JPhi1618 for reminding me to add the actual reason this works