No, you remember incorrectly.
I was relegated to the lowest tier - i.e. I was getting only full fleet updates OTA (so this Christmas 17.50.2 update and the 17.24 in August before it), anything in between and I needed to ask my SC for the update at a time of service, and they said it needed to go to Engineering to be approved (And that did not happen every time - i.e. there were times I asked for a firmware update and did not get one without any explanations).
Full OTA block typically happens for salvage cars, though. Once the system is flagged as a salvage (they have some markers even if no airbag deployments) - no new OTA updates for that one until you drive the car to the ServiceCenter and they can make sure it's all fine and manually take you off that blacklist (could non-salvage cars end up on that list? probably so, bu I do not know of any).