Exactly. I posted elsewhere that a constitutional arrest must be based upon probable cause. However, various states' statutes as well as elements of due process do authorize law enforcement to detain someone and to otherwise take them into custody. From the subject's point of view it can be argued by one's attorney that one believed they were under arrest once law enforcement deprived them of their freedom of movement.

It can be rather complicated. Thus, I encourage everyone to withhold judgement.