It's not considered bad form to race the final stage. It is consider a waste of time and unnecessary if the standings are well established. But if there are a few seconds between top contenders, expect them to race for the time bonuses for sure, if not the stage like Vino did last year to snag 5th from sleeping-at-the-wheel Levi.
Actually, in all fairness to Levi, last year was a mess. Due to rain, they canceled the time bonuses. Levi reasonably assumed that including canceling the time bonuses at the finish, not just the intermediate time bonus when they enter the Champs D'Ellysses. Not sure if Vino had better info or if he just was trying to win the stage and got lucky with the time bonuses. In any case, Levi was probably powerless in terms of doing anything about Vino winning.