i also recall reading stories of how the "hunters' of the time were casting with zinc in their lead,to add to their hardness for penetration.
once the full metal jacket [full patch] hit the market a lot of the old went out and the new came in.
then came over penetration [here in the states] and jacketed bullet development went hay wire.
with over expansion and poor penetration being the common theme.
so you just used a heavier bullet for better penetration.
just because there was more mass to carry on through the animal,this was where elmer got the bigger is better for elk from.
if you expand you can't punch through,and i think this influenced his cast boolit designs also.
maybe just maybe his designs are better for bigger animals like elk and he figured the straight line thing was fine [compromise] for deer too.