That doesn't really excuse the issue here. I'm fine with that ruling applying to situation, a cop asks you to step out you step out. I also do place blame on the driver for just taking off which only made the situation worst. I still take issue with a cop walking up to the car and going "Hey I know you, you are under arrest" then l either lying or being mistaken about that person having a warrant. He's either incompetent or a liar, and chances are if he had his way that person would be going to jail for the night till things got sorted out. I am not ok with that, innocent people should not go to jail because a cop failed to do his job properly, or even worse, lied to place that person there.
You'd think he would at least detain and verify first instead of jumping straight to taking the person to jail.