It sounds to me like the cop was young. Bruce may have had trouble with a balance test or two and was arrested. It also sounds like there was no other experienced officer there to advise the officer that de didn't have to charge him and could issue a summons for the stop and articulate in writing the basis for the arrest eg: lost balance on a one leg stand, after all Bruce does have a bad back which I can identify with. An experienced officer asks those question before testing. eg: are you on any medication? Do you have any injuries? Did you graduate high school? Do you have any speech or cognitive difficulties. etc.
I hope all those sanctimonious peeps on the other boards choke on their words. I really do.