“So if a cop arrests me, I can turn around and go home, right?”
No, and he can wrestle you, cuff you, Tazer you, etc to keep you from leaving. Arrested means no longer free to leave. A whole set of law swings into action ref your rights, and what the officer may and must do.
For example, the famous Miranda warnings. Two conditions trigger those, you are being questioned, AND you are not free to leave.
If the officer wants to question you,, but would permit you to walk away, Miranda is not required.
Basically, when you are free to leave, you are not arrested. If Rand would have tried to walk, the government agents would have physically detained him for the police. THAT is an arrest.
Another way to think of it is this,, when the Walmart employee wrongly thinks you have stolen something, and tackles you, holding you down till the cops come, you will be suing Walmart for “false arrest”.
I can’t say I am sorry for him..