It is a crucible graph so it should be fairly accurate. I know what you mean though Pitman because I had a heck of a time reprofiling my YKLE even with a coarse diamond hone so it certainly seems like it has decent edge retention.
My best guess is the modification that is done to make S7 SR77 bumps up the edge retention. Probably with a bit more carbon. Also the Busse heat treat can only help.

Knifeguy you are probably right about 10V and S7 but I won't let reality spoil my dream.
There are tons of good reasons why you can't get good results just throwing stuff together from a graph.

One of the most interesting steels on the graph is 440C. It has always been one of my favourite steels and this graph shows why. It is very close to D2 with just a tiny bit less toughness but way way more corrosion resistance. It is an awesome steel for certain purpose. It is hard to work with though.