There was some fuss about it at one time. When Hodgdon took over distribution of the Winchester brand, the agreement included that Winchester's owners, whomever they might be at the time, would keep testing and load development up to date. They didn't, so a lot of old data still rides with the brand.
As to why that pressure is so low, that's going to be a matter of speculation. Cases have changed over time, and I note that if I use the smaller capacity found in some older cases and that is Quickload's default value of 28.8 grains of case water overflow capacity and use the 0.704" length of the Winchester Pointed Soft Point bullet in their original loads, then 26.3 grains of 748 has 99% loading density with QuickLOAD's default powder bulk density for 748. So they simply may not have wanted to get into compressed loads with it. More recent Winchester cases (post-mid '90s) have more volume (30.1 grains case water overflow capacity) and 27.6 grains of 748 would produce that same loading density in it.
Hodgdon had to substitute an available Speer Soft Point for the unavailable Winchester bullet in their data. They found one the same length but they have it seated deeper to 2.200" instead of 2.260" as is in the old Winchester data. That would partly compensate for more capacious cases. Gordon's Reloading Tool gives 748 a little bit higher bulk density than QL and says 26.3 grains would be 98.7% load density in the modern capacity case. GRT also gives higher pressure and velocity, so the modeling isn't a perfect match to the lot of powder used to accumulate the original Winchester data.