I am curious what and where you have read this Art. I think you likely made some semi-false assumptions based on some info you have read. But, this is an assumption on my part.
From what I know about M4, it is in HIGH favor with a lot of competition rope cutters. Their knives blades are long, but I don't think toughness is nearly as important to them as sharpness. I think "Sufficiently" tough with much higher emphasis on edge retention and edge toughness is more important to the competition guys.
That's what I meant, long. I am pretty sure the toughness can endure the basic camp chores of chopping and batoning with the added bonus of longer edge retention. The numbers are probably not that far off from SR101 but if there is a huge difference in price(like double) then I can see how it doesn't belong in the Yard. Honestly, I think it would make for a killer machete but I think you are right about it being more adept as a smaller blade. It always comes back to price vs performance and so I do believe there is hope for it as a Yard blade but it would have to be small. Maybe that orange mudder design that HD has been talking about.
KS, I don't think that graph you linked showed M4, and I think it showed S7 as being the toughest. SR77 is S7 with awesome heat treat if I'm not mistaken.
