I agree, esp. with currently studying "Human Growth and Development". BUT...I think LBS's do it - remain friends - because it's less painful. Friendliness towards WS brings friendliness back in some cases. They mistake that for the WS changing their mind or coming around. Maybe it is in some cases, not for me to judge. When LBS dares not to be nice, WS's get angry at times and say things or do things that hurt the LBS. That causes the LBS pain. It's EASIER to be nice: nice equals less pain. However, nice doesn't garner respect when WS is doing things he/she should not be doing!
Therefore, to me, being friends is counter-productive to trying to save a marriage. I think it's Sandi's tagline to "do what works, not what feels good"
So - why the story about remaining friends on the homepage? Why would anyone endorse positively reinforcing negative behavior???