The Hawken brothers weren't the first to use 1:48 twist. That was a common twist going back to the late 1700's. It wasn't until Thompson Center started making their so called Hawken rifle with that twist and shallow grooves that it started getting a bad rap. And I'm not sure how much of that was really justified. A lot of shooters somehow managed to win a lot of contests with their TC rifles and patched round balls.
Herb Troester performed an interesting experiment with his copy of the Bridger Hawken he made himself with a barrel that has a 1:48 twist. He seemed to be focused on measuring muzzle velocity and spread and point of impact rather than accuracy, but looking at his targets, he got about the same size groups for charges from 84 grains up to 210 grains. I think his experiment demonstrates the versatility of the 1:48 twist assuming it has sufficient groove depth. His post can be seen by following the link below.
The Horace Kephart Hawken
I don't think there is an answer to the OP's question. The patched round ball is pretty forgiving and often gives good accuracy in a number of different combinations.
The slower twists such as 1:72 and 1:75 came about in the 1970's when a lot of people were trying to turn their muzzleloaders into magnums with real heavy hunting loads.
For example, below is a list of the recommended loads that GRRW included with all their rifles in the 70's. Their light load is my hunting load. Their moderate load is more like my max load, and I have never loaded up to their maximum load. But this was representative of the mindset of hunters out here in the West in the 70's.