I was sort of vaguely aware of this but thank you for pointing it out! I think the point still stands, and that reference counting like this is just a different kind of garbage collection.
It's not exactly like that there is cursor inference and copy elision. But ok...
It certainly adds (some, not many thanks to static analysis) runtime checks, but it's also fairly distinguished from typical tracing garbage collection by being deterministic. I believe ARC/ORC also works with a shared heap via "isolated" data.