What I haven't seen in all that reading is the people who complained of poor braking didn't make any mention of whether or not the car had rear wheel cylinders replaced in the recent past. So they make it sound like install the RPV and problem solved. Without that information we can't possibly make an informed decision that wheel cylinders are the cure, or aren't for that matter.
I personally can't put a lot of stock in that simply because, I'm not there, I don't know the history of the car itself and I feel there is a lot of missing information. I also feel rear wheel cylinder relplacement was never mentioned in any of those posts because the updated wheel cylinders weren't brought to light until the very last post,,,then the posts go dead. As if that's almost like an "AHA!" moment.
While all this effort is admirable, I don't see it as necessary just based off what I've found. I listed my experiences, that was just on some of my personal cars. I've also done complete restorations on customer cars, all kinds of brands, including complete revamps of disc/drum brake systems and I've never once experienced any of these issues that are being discussed here. I would never let a car out the door with subpar brakes for obvious reasons. At the same time however, I'm also replacing wheel cylinders. That says a lot to me but of course you have to make your own decisions.