Is it true that oil-free moisturizer causes the skin to produce more oil for someone with combination and oily skin (or anyone for that matter)?

Not likely: The moisturizer mostly stays on the skin surface and its major function is to slow down the evaporation of water from your skin. Usually the body oil serves this function but the oil is washed off by bathing. If you have an oily skin, you should avoid using oil on the skin but oil-free moisturizer would not cause you to produce more oil.