They are compatible with DDR3, not a specific frequency.
What you are referring to is that if your CPU is NOT overclocked you can't get over 1333MHz for your RAM.
So if you bought 1600MHz RAM it would run at 1333MHz unless your CPU was overclocked. If you brought the RAM timings up to 1600MHz you'd need to overclock your CPU by 1600/1333 or 20%.