I have never had the priest ask me about the subject of my lustful thoughts. To be honest, in the climate of priests committing sex crimes in recent decades, I would have been leery of any priest pressing me for details. At the same time I am not one to have any unusual lustful thoughts such as incest, bestiality, or SSA beyond a momentary crush or two when young that I didn’t act on. My lustful thoughts have been 95 percent plain vanilla stuff. I have confessed it by saying “I’ve had some lustful thoughts twice” and left it at that.
I tend to think if you just have a stray thought once in a while and put it out of your mind quickly, it’s not worth giving details. If on the other hand you have a pattern of say, incestuous thoughts going on, this may be something to take to the mental health counselor as well as mentioning it to the priest. Keep in mind that the priest is not there for mental health help and if you are having repeated thoughts of a disturbing nature, you should be getting some psych help for that, not just expecting the priest to take care of it all.