Yes, I agree, but I also know that such a major job costs a lot and many of us cannot afford to to this sort of thing. In an ideal world........In the meantime, I would guess the homeowner needs to just keep scrubbing away, until the wall surfaces are in decent enough shape to prime and then paint. OR - IF they like wallpaper (I dont!), that would solve a lot of issues here.
I used to own an 1860 Victorian home - a five-family home- in Cambridge, MA. It had not been well cared for. We bought it and started renovating it, all on a budget. Those were serious, SERIOUS walls, made of old fashioned plaster AND horsehair. Yes, horsehair.. That's what they used to mix with plaster to make it stronger. It worked!!!!! It was fascinating to uncover layer upon layer of ancient wall papers, until we finally found the real plaster wall. I removed all the plaster covering two old chimneys, and found the most wonderful stuff inside each wall! Old newspapers, antique bottles, a ring, a bird skeleton, a coin, nails....all kinds of odd things. It inspired me to leave a time capsule for the NEXT renovator!