Ray, different metering systems will give different results in exactly the same way that anyone who wears two wristwatches, will never know the correct time.
I have a couple of F3 cameras and an FE2 as well as a spot meter attachment for my Gosson Profisix. The spot meter attachment gives me 1, 5 or 10 degrees area. By using a long focal length or a telephoto lens, I can emulate the spot meter reading area with the Nikon bodies, or I can walk up to the subject, sometimes.
I have used a Nikon FA which was the first camera with the matrix metering system. I believe that the FA matrix metering system won a manufacturing award from the Japanese government. This was not a photographic industry award.
I tested the FA camera with a view to add it to my arsenal, or replace the FE2. At the time my reference was my first F3 and my standard Profisix. With these two meters I had a standardised exposure and developing system that worked reasonably well. I was shooting slide film so my exposure had to be quite correct and consistent.
With the FA, I found was that the matrix metering system gave a different reading, different enough to require me to adjust aperture settings to obtain near identical results to my other cameras. I didn't bother to purchase the FA.
One important note with the FA camera and it's matrix metering system, it requires AIS lenses so that the body knows the focal length of the lens. This may or may not be a feature of the different readings being obtained with later Nikon bodies that also incorporate matrix metering. I'm not very knowledgeable about much Nikon stuff past the F4, so I don't know, but it could be a point of difference.
My F3 bodies match very closely, my Profisix. I know my Profisix over the years may have drifted, so may the F3 bodies, but I don't think so.
I have over time been with other photographers and the Profisix readings are virtually identical to the latest Sekonic digital readout light meters, this suggests to me as well as the film I develop, that the F3 bodies and the Profisix are reasonably correct.
I'm not entirely certain about this, but I seem to remember hearing/reading many years ago, that whilst the F3 and most hand held light meters were set to a middle grey or Zone V, quite a few other camera bodies by various manufacturers had metering systems that over exposed slightly, up to about 2/3rds of a stop.
I believe the idea was that as nearly all cameras were using colour negative film, slight over exposure was far better than slight under exposure. I know for sure, that a slight over exposure, around 1/3 to 2/3 of a stop on C41 film, gave finer grain and greater colour saturation possibilities for the automated printing systems of the day.
The last thing in favour of the F3 camera body and it's metering system, is that it was the first electronic professional body released by Nikon, they really had to get it right, or lose to Canon. There was unbelievable money at stake, as well as pride. Nikon got it right that time.
The F3 body with it's 80/20 metering system in the hands of someone who understands metering, can be more accurate than a computer memory matching system in many cases, not always, but almost always.
My two bob's worth!
Mick.