If an algorithm can be (and is) designed to tell you how much ink is being sprayed onto paper, it can also be designed to tell you how much ink is going into the maintenance tank. You only know with certainty how much is being wasted by knowing how much is being wasted, and you only know how much waste can be reduced if the manufacturer tells you what's being wasted and also tells you how to manage the printer to minimize it. Both companies are not doing either and both companies are capable of doing both. In fact back in the days of the Epson 4000 you got total ink used on each nozzle check printout, so you could subtract the latest one from the immediately previous one and easily see how much ink for all purposes was used for what you printed between nozzle checks. But they disabled that information by the time the 4800 came out (maybe because I made public use of it on this website - who knows). And if I remember correctly what I was told about CO use in the Canon Pro-1000, for this one "ink" only, the Accounting Manager reports total consumption, not just the amount sprayed on paper. If so, why not provide it for the other inks? There's been no technical explanation I've seen or received from either company about why all usage can't be reported.
As I've said, this may not be a big deal for some people, it may be a bigger deal for others. It's quite OK for you if you're happy just knowing total ink consumption for both purposes and you are willing to set up an accounting framework for doing that, recognizing that the cartridges expire at different times as you create more prints, making it necessary to do stock-flow inventory accounting - I know because I've gone that route. Other people may prefer a more direct route to the information that makes printer management more transparent and easier. That said, it's obviously not a burning issue to the larger user base, otherwise the manufacturers would have most likely addressed it by now. I'm leaving it at that, because I think we know the issues at play and we've kind of exhausted them.