I love Dr. Jan Morton. She is an amazing advocate for breastfeeding. She also is involved in improving education of medical students and residents. Personally, I don't agree with her on this point. However, it is not an unreasonable point of view to dissuade cross feeding. La Leche League also does not support it. My point is don't demonize her for this one point. She is super knowledgable about breastfeeding and has helped countless women to succeed at meeting their breastfeeding goals.
I was surprised, how ever, that she didn't go into the low milk supply issue more. Perhaps that was an editing decision, it wasn't the main question being asked. On the Stanford website, Dr. Morton has lots of good info on breastfeeding and pumping, including info on milk supply. I would guess she is more knowledgable than some IBCLCs.
http://www.breastfeeding.com/all_abo...orton_bio.html