Also, we need not work under the assumption that the rehab phone call was stupid mistake or blunder. Until we have all heard the 911 call AND learned where JB and SG went during that 15 minute trip within the community, we can't eliminate the possibility that the phone call was a smart, rational, and somewhat calculated move to make. The killer could have made that call to try and regain control of the situation that slipped free of his grip.
"you can't kill me because they will know it's you"
If SG in a last ditch effort to protect herself somehow communicated to her killer that she had informed her family of his identity or address or both, which would be the logical defense mechanism for a victim who knows their attacker, then the call could put him back in control.
There was a good deal of time that she knew someone was trying to kill her and we know that she was able to call 911. So it is likely, in my opinion, that while dealing with her attacker, over the phone or in person, she would use this method to try and defend herself even if she knew she hadn't informed her family. We also have some reasons to believe that the killer may have told SG he was LE, so it would make more sense for her to threaten him with "I told my family who you are" than "I told the police".
We are without a doubt dealing with a predator who thinks a few moves ahead of his prey, but what occurred that night wasn't the typical operation and the scenario slipped out of his control. I believe SG was a very smart and savvy person so much so that she did outwit her attacker to the point that her actions/moves will be responsible for his demise.