You may be completely devoid of thoughts or fantasies during sex at some times but have wildly erotic images flashing through your head at other times.
This is what a colleague of mine refers to as the “fuel mix” in sexual arousal. For the non-addict this fuel mix can vary a great deal from time to time without being problematic in any way.
Sex addicts get hooked on particular sexual fantasies
For a sex addict, the sexual fantasies that lead to arousal and orgasm can be quite predictable and relate to the particular kind of sexually addictive behaviors that the addict most prefers. It’s not necessarily that the fantasies are deviant but rather that they become rigid and predictable.