Swift has a GC, what it doesn't have is a tracing GC.

Technically it is a form of garbage collection. However, garbage collection is a very broad term that arguably encompasses even C++ smart pointers. Typically one refers to a garbage collector in the meaning of a separate process that runs independent of the application. Either in the background or “stopping the world” to collect. ARC is part of the application code. It is also visible to the compilers optimizer, which can optimize away redundant redundant reference count operations.

Typically one refers to the CS definition of automatic memory management, using accredited references like "The Garbage Collection Handbook: The Art of Automatic Memory Management".

Everything from "ARC" is there on chapter 5.

In your division, ARC is stop-the-world variety because things like cascading deallocations cause unbounded work.