As a cult, they have to create and maintaing a control mechanism where their followers do as they're told. Softening the df rule isn't going to happen because what if you could talk to your df son or mother anytime you wanted to, what if you could talk to your friend who was just df? Well, what's the big deal if you decide to do something that might get your df?
Simple, if df'ing is ineffective in controlling sheeple then more will do as they please and soon you'll have many walkng away from the cult without fear of losing friends and loved ones.
Another point is that df aren't on the same level as apostates. DF ones can be kicked down and pushed around by wts bullies knowing these people will try to come back and believe that df is for their own good. Apostates don't take this shit from them, and we are viewed not as df might be- even though some have been df, but rather apostates are viewed as ones to be feared of corrupting jws' faith - since their faith is based on load of shit and obviously can't stand to any questioning wts tries to keep jws from any and all communication with apostates.