As others have said this is misleading and inaccurate. GCD, which will be cross platform as of swift 3, is very pleasant and robust to work with and abstracts the threads, mutexs, and dispatchers away from the developer. PromiseKit and Venice are third party libs that also provide other better concurrency patterns.
Also GCD can be faster than locking with a mutex because it doesn't have to trap into the kernel. So now in my app I tend to protect access to variables with queues instead of @synchronized. The only downside is that it can't replace recursive locks
