Whether reference counting is GC or not is arguing about semantics.
But correctly implemented reference counting is essentially pause-free. It's consistently "slow", which is better for some cases that unpredictably "fast".
IMO it's not just semantics, rather, GC is too general of a term if it includes ARC. In terms of performance analysis the two are vastly different. One has basically an unbounded worst case but a good average case, the other is the opposite.
Reference counting also has an unbounded worst case: what if you drop the last reference to a very large graph of objects? Then you free the whole thing, which can take an arbitrarily large amount of time.
