It's all a matter of priorities, not tech literacy. He has never been very much into tablets and in a way I admire him for sticking to a device for over 10 years, just as I admire people still using an iPad air 2 (and the fact that the iPad air 2 was supported for much longer does not change much in the end, since Android remain compatible with apps for longer and security has never been an issue on a tablet for someone with some tech common sense).
He still uses device on old OSs like Windows 7, although not connected to the internet, and again I admire him for that.
As for not updating to 26, he has no way to know other than reading feedback and the feedback is maily against 26. I personally don't feel there is any loss of perforamance or battery life, although the accidental resizing tends to annoy me and that's why I have kept most of my iPads on older versions. If Apple allowed slide over on the non windowed mode, I would upgrade everything.