Frustrating I agree. However, I think that the title of this post is a little misleading in that it isn't so much a law that is supposed to tell all victims it is okay to tape the conversations but rather legitimizes the recordings to be admissible if they were recorded surreptitiously. Granted, hopefully victims will also become aware it's okay to record, but I think it fixes that problem of admissibility and the whole thing about "can someone unaware of it" be recorded legally.
Several states have laws about this. One party knowing - okay, other states say it has to be both, and so on. Remember Monica Lewinsky's conversations with Linda Tripp? She got into trouble with that same sort of thing.
Linda’s taped calls had an added complexity if I recall, she was taping phone calls (not a personal encounter) AND there was a squabble that she was in a locale that permitted citizens to tape a call without disclosing it to the other participant while Monica was not.
Some places only require that one of the persons need to know that the call is being recorded.