There is nothing special about the lug nuts. If the OP has 12mm studs I'm sure you could find the same lugs and they will work fine.
Your missing the point, the 570 Full size utilizes the same hubs, nuts and studs as the 900. So the 900 LE wheels, should and do fit those units, which is evident in your pic.
The OP has a 570 MID SIZE, it has smaller lugs and studs ( 10 mm) and different hubs.
And yes, there is nothing special about the standard 60 degree tapered lug nuts on the Ranger.
The LE wheels that the OP wants to put on his unit are designed for the 900 Rangers, using 12 mm lugs and studs, which means the stud holes as well as the lug nut seats in the wheels will be larger than for the 10mm. The diameter of the bulge on the 12 mm lug nut is larger than the 10mm, so using the 10mm lug nut decreases contact area on the lug nut seat in these wheels. Therefore the 10mm closed style ( and possibly the open) lug nut could bottom out on the stud before you could torque it to spec, since it's smaller, the diamentional difference will allow it to engage into the stud hole further. And with all the different diamentions combined this reduces the contact area of the lug nut bulge to the wheel seat. Which on a lug centric design, is what is holding the Ranger up, and centering the wheels. This way there is a lot of additional vertical force being put on the studs, so it is possible for them to bend, break or shear off ( can this happen with the 12mm, sure it can).
And I haven't even covered the hub bore diameter in the wheels.
Since I am not that familiar with the 570's, I would like to see a pic of the (570 Mid) wheel hubs for clarification on them utilizing the hub centric or lug centric design.
There is also a safety issue that is present here.