I think here multithreading is confused with parallelism and concurrency. They're not the same. Concurrency guarantees two processes are happening simultaneously while multithreading does not. Multi-core processors offer the possibility that two threads can be processed independently and intel's Hyperthreading can make multithreading on the same core really close to multiprocessing or concurrency, it is not. When two threads are processed by the same core, this is done serially and not in parallel.

In a Nutshell

parallelization > multithreading