I don't want to go over old ground about grades of steel, but somewhere in all this is the difference between old steel and new.
Go back a century to when 'cast steel' was the norm. If you wanted an all-round chisel you needed something relatively thick - so you bought a square edged chisel. If you needed something lighter and more delicate you bought one where quite a lot of the steel had been forged or ground away - a bevel edged chisel. But you could not expect to take a heavy cut with it - you'd risk snapping the fairly brittle chisel.
Modern chisels are made of steel which is much tougher, so less likely to snap. You can have something strong enough to use as a general purpose chisel even if the edges have been ground back a bit. Overall, the thickness is a bit more than an old, delicate bevel edge, but almost all of the time the extra thickness won't be a problem. So we get true general purpose chisels tough enough to chop a big rebate but usable for common dovetails as well. Some people even chop mortices with them.
The only time I can think of that you really need a fine land on your bevel edged chisel is when you are cutting really skinny dovetails (as found on old drawer sides) where the chisel is the same width as the cut, so must cut right into the corners without being held at an angle.
I don't recall those beautiful, wide dovetails of Derek Cohen's work being over cut...
