If he invites lustful thoughts, etc. then it is acting. Being visited by feelings is not something done wilfully, and cannot be sinful. Christ speaks of "committing adultery in his mind", -- he is describing an act of mind, not an inclination.
I happened to be reading St. Basil's rule concerning nocturnal emissions and he said... oh, sorry, family forum.
You are making a fine point, a fine line of difference, but a line nevertheless IMHO.
I forgot to add. I read somewhere long time ago something about the difference between having a thought and chasing that thought. I think it applies a bit.