And, honestly, they didn't even need to have given him the field sobriety test - they could have sent him home or driven him home then. They chose not to.
As a favor? Is this suggested by police training in most locales?
Especially in times of heightened tension and trouble. Save the jail space.
I got pulled over for failure to stop for a ped in a crosswalk. (Turned out the ped wasn't trying to cross, but so what, right?)
My registration was expired.
Instead of taking me and my car away, the police let me move my car off street to leave it there and to have a friend come give me a ride.
Nor is my story unique. This is how police do things in many places.