I don't pretend to have tried, or succeeded with, every technique under the sun, but I do know what has worked for me (or not). Having installed, filled, skimmed (in some cases) and decorated almost 100 PBs on one project alone, I can speak with some experience. And I certainly appreciate that a lot of what is posted on forums is (if one discounts the purely abusive or insulting) of debatable value - but there are many postings based on tried-and-tested experience too, albeit not necessarily giving the only or best solution. But technology moves on, as you indicate with (some) paint - Barry Bucknell would be a fish out of water in many modern DIY settings! I shall try SBR on walls next time a relevant job comes up.
As to priming plasterboard (before joint filling), you said above: 'My conclusion then, is that any prior preparation to [plasterboard] is a 'nice to have' rather than 'need to have'. Allowing for the missing word, was this not at least a recognition that PB could usefully be primed? But we can both agree that it need not be and really should not be, except (in my view) to harden/reinforce broken/abraded areas.
I'll rest my case there.