That is interesting. Like Malhar, mine is a regraft from the original Citrange rootstock to a FD rootstock, done mainly to dwarf the tree, since Satsumas here require robust winter protection some years, but also in hopes the FD rootstock would give somewhat earlier ripening, since the original rootstock produced fruit which were large and well colored, but quite sour. It was done three years ago. The first year I knocked the fruit off to enhance growth. Last year one fruit, a bit sour. This year half a dozen.
But I also wonder about cultivar variance. I have four producing early ripening Satsumas. Xie Sahn, LA Early, Early St. Anne and Miho. The LA Early and Early St. Anne have been in the ground for over a decade. The first three are bumpy and thick skinned, with that stem end bulge, but Miho is smooth thin skinned. FWIW, my Changsha, while not a Satsuma, is also smooth thin skinned and early ripening.