I think one way to look at the "car girl" situation is as an indication that the main girls' content will be slow. Devs often give you some throw away sex with side girls early on as an appetiser to hold you over until the main (course) girls are served. Sometimes it is in dream format, or shower fantasy, etc. While I personally very much appreciated the car girl content, I know some people don't want those kinds of scenes. That said, it is important to note that I believe one has to specifically pursue sex with her in order to get it. A player can't really stumble into it and be overly surprised. She was horny for and receptive to the MC from the very first meeting. AVN rules of attraction apply...of which I am thankful.