I have to admit that while working in a nursing home for two years, we often saw this "surge".
Many times, people who were bed-ridden, or totally dependent while up, would take a turn for the better, only to die in a couple of days. It was something that we saw so often that, if a patient was doing better than usual on a Friday, we weren't surprised to hear that they had passed over during the weekend.
I've watched my aunt die at 57. Totally healthy to the usual outsider, but suffered sudden cardiac arrest while shopping. After being in a coma for two weeks, her fever went up to 108. I used a cool cloth on her face and said my good-bye. One tear fell down her face. As soon as we left the room, she took one breath and died. My grandmother also did the same. She roused, asked for us, and then laid down and left. My mother was fine and had just told the nurses that she felt no pain. I stepped out for 45 minutes and came back to see her gone.
It's not uncommon at all for our loved ones to feel comfortable once we leave the room, and then let go.
Mandi