Thanks for your detailed and thoughtful comments, Cris. The post was primarily motivated by the way this so-called policy was implemented at my university. Unlike yours, there was no trial, no communication with students (or staff for that matter) before it was implemented, and no thorough policy development process.
Had these occurred, it is likely my objections would have been addressed, and I would not have argued the case, let alone publicly. As it stands, the semantics of what turnitin and its supporters call it versus what objectors call it matters little when it is implemented in a punitive, dismissive, non-communicative manner as it was in my case.