While there are some major similarities between doing porno and escorting, there are also some important differences. Phoenix can pick and choose ahead of time which roles she accepts and who she works with to a large degree, on a closed set with a director and the semblance of a "script". In escort work, not nearly as much. Sure, she can turn down a client at the door based on whatever criteria she might employ, but that's lousy for business unless the guy is clearly loaded, disfigured or threatening.
That said, invoking "love" as her reason not to do escort work, doesn't really add up when she's perfectly willing to have all of her orifices stuffed and serviced by both men and women who are essentially strangers anyway, on camera and for money. The love angle doesn't really add up in my view (with the exception of dinner dates/overnights/weekends), probably more of a throw away excuse to keep her fans/client wannabees off her back. My guess is she has other reasons for avoiding escorting.