This is starting to make sense to me. I don't think I've ever seen a serial cable that delivered data and also power. There are however USB cables that deliver data and power.
That being said, I think you are right that you will have to get the other cable so that you can deliver the power and data. Or just connect power and data separately.
@nokones expressed it well. After hurricane Beryl, the only coms I had for a few days was GMRS and ham radio which worked very well. But that was NOT an SHFT situation and there were repeaters that were still available. Under a real SHFT, radios may not be as useful as we would like.