Task manager usually doesn't show the overclocked frequency when the CPU is loaded, for some reason it only shows the stock speed. I know because I have overclocked my 4770k and the task manager only shows the stock speed, even though other programs show the actual speed it is running at.
In addition, whether or not your CPU is overclocked, if it is not very busy or not running demanding tasks, it will power down to a much lower clock speed in order to save power. So if you're not demanding a lot of your CPU, such that task manager shows it running at, say, 25% of all the cores/threads, then yeah, the actual clock speed will be much slower than the maximum or stock speed.
So if your system is idling, it certainly won't be running at 4.6 GHz. Why on earth would it? It has nothing to do!