Yes, that adds up - and I believe all 024, 026, 240 and 260 came with a mini spline drum.
As I see it, the only point with the mini spline is that a 6-pin picco rim is possible (I don't know if they currently offer them)- besides just being different, to sell more premium priced Stihl branded parts .
Btw, also the Stihl branded 7- and 8-pin picco rims are normally availiable only for the mini spline drums, which likely is a result of a deal between Stihl (that sell them) and Oregon (that make them for Stihl). Pin type rims have been made by others in the past though, at least Danzco, for other spline sizes.
Every 026 that I have seen and came my way had a mini spline on it if it was original, a few have had the drums replaced with the Oregon replacement and run the larger spline we usually call ,small spline. Seems the 026 is stuck with either the 7 or 8 pin drives in .325 mini. I took measurements between the mini and the small rim drive rims. Across the largest parts, at the outer edges of the splines on new drive rims,
OEM Stihl mini= 19.73 mm or .777 inch, the small spline OEM Stihl rim= 21.30 mm or .838 inch and the Oregon small spline was a tad larger at = 21.35 mm or .840 inch. It is easily seen that a small spline rim on a mini spline clutch would be very sloppy.