Taking those in reverse order, it doesn't matter what the statute says.
Court decisions have said that if the person does not feel free to leave they are under arrest.
And while they do have an ID statute, it's just like most others in that it only applies to people whom the officer has RAS of committing a crime.
But since open carry (or indeed, any carry outside of circumstances where a license is required) is not RAS of a crime they had no lawful reason / authority to stop & detain him, let alone demand ID or steal & search his property.
I agree with everything you wrote, with one small exception.
The poster who started this thread wasn't stopped by the cops for open carry. He was found sitting in his vehicle for a prolonged period which the cop interpeted as suspicious activity. The poster wrote that the cop said it looked like he was "casing" a store. Thus the cop has the required RAS to both detain the man and to demand ID.
This case arose when the cop observed the man engaging in conduct which appeared to him to be the casing of a store for a likely armed robbery, or perhaps stalking an ex-girlfriend, or whatever. Upon approaching the man, and stating his RAS, and demanding ID, the officer was refused the identification. The officer then arrested the man for refusing ID, and searched his vehicle, and found a firearm with an altered serial number, and charged him with (9.32.030) possessing a defaced firearm and (9.32.040) defacing a firearm.
I'm guessing the RAS will be determined as legal. While it is not illegal to simply sit in your parked vehicle, the cop will claim the "totality of the circumstances" (parked in a suspicious location, being there for a prolonged period of time, acting cagey when questioned, refusing to produce ID, etc.) justified the detention/arrest. Keep in mind that when the cop approached the vehicle and ask the man what he was doing, this was only a mere CONTACT. The man wasn't detained/arrested until he refused ID and was handcuffed.
Hopefully a good attorney will be able to get the evidence thrown out, claiming the search was illegal, but I doubt it.
IMO, the man's best bet will be to cop a plea to one of the two charges with a deferred sentence. In order for a a defendant to get a deffered sentence he/she must plead guilty to at least one of the crimes they are accused of. In other words, the promise of a deferred sentence is often traded in exchange for a guilty plea in plea bargains. Deferred sentences are usually only given to first time offenders, or to those who have committed relatively minor crimes, or for those cases with weak evidence. If the defendant fulfills the stipulations surrounding the deferred sentence, the case is dismissed and the incident is cleared from their record. If the defendant violates probation, he or she must serve the full sentence immediately.