I had recently asked in a zone system thread if anybody had compared zone system with matrix metering in practice and based on the responses I got an impression that none had.
I have. I went through the whole film testing regime of the BTZS. Did all the densitometry, ran everything through the computer program and have the charts of contrast, effective film speed, developing times etc. Bought the app for my phone, and it can accommodate two ways of metering: incident and spot.
As a test, I picked a scene that had a full range of tones from deepest shadow to a white fence and did it near noon on a cloudless day where there was constant light. Metered according to the way the BTZS system tells me, and entered it into the app. Metered both ways, using two different hand held meters (incident and spot), and then as a check used the Nikon F6 matrix metering. It exactly agreed with the other ways of metering, but obviously is much quicker. It basically does the same thing as finding the scenes' brightness range, but also goes further such as ignoring an extra bright highlight like a reflection off water or chrome.
I've shot many rolls of E6 through the Nikon and the metering has never let me down. The best part is it's smart enough to detect colour as well, so knows when I'm taking a photo of snow for example. My hand held meter doesn't know that, so I have to guess at the reflectivity of the snow and estimate the compensation in my head. As you said Drew, for 8x10 E6, I'd rather know, than guess. With a hand held, I'm forced to guess.
Sure, the matrix metering an algorithm, but so is the zone system. The margins as you call it comes from film testing, including the metering system. It all plays a harmonious part in getting the correct exposure on film. I've done enough testing now to know the F6 will get it right in every type of scene I photograph.