The reason for the long grind is to get the cutting angle low, 15 degrees in the case of my weaver. Blade is 1.86" along the bottom flat and .5" thick on the spine. Shorter grind equals steeper angle and a steeper angle makes for a harder pull. I notice this a lot with a few of my old round knives, a small Rose that has a hefty shoulder is more difficult to push than a small Gomph that has a fine thin taper, that one cuts like butter. Both knives are very sharp, just that thicker blade on the Rose has to push more material aside to make the cut.
The bimetal blades were probably made for cost savings way back when, not sure if there's a good reason in current times for a bimetal splitter blade other than sharpening might be a touch easier by only have 3/8"-1/2" of hard steel to grind. Bimetal splitter blades have the leading edge as tool steel, not really "within" just leading the way.
Just my views
Jeremy