No, "we" never knew how "aware" these patients were. Speaking for myself personally, I never knew; I've never been in a PVS but I do affirm that any person who is in a PVS deserves dignity, the right to life, and the right to ordinary sustenance, such as food and hydration.
I lived through the very traumatic case of Terri Schiavo, whose husband hated her guts and really, really needed her to die ASAP. But I only recently learned of Karen Ann Quinlan, whose parents were quite devout and merciful, and had perceived that the "treatment" (a breathing tube) was causing much discomfort and distress to Karen, yet the medical establishment insisted that removing the tube would be "MURDER" and they engaged in a protracted legal battle against the "MURDEROUS PARENTS" who simply wanted them to withdraw this barbaric medical treatment.
https://en.wikipedia.org/wiki/Karen_Ann_Quinlan
Karen's level of cognizance was fairly obvious to any observer: that she was feeling pain and distress, that she was capable of emotion and rational response to stimuli, and that changing those stimuli resulted in distinct changes in her responses. That much is true.
Karen Ann Quinlan's quality of life improved immensely after the tube was removed. She began breathing on her own. She lived a good life (in a PVS) for a significant period of time and was not, in fact, ever murdered by her loving parents or by her physicians.