Pretty sure only difference is the S1200KPR supports the low end IB Xeons like the e3-1270v2.
I think you’re right. Looking at the latest BIOS release for the S1200KP, the release notes say E3 v2 only on the S1200KPR.
It’s too bad it requires a separate board for that. Other C206-based boards such as the Asus P8B WS can use Ivy Bridge chips with only a simple BIOS update.
A comment on the original article confirmed this from an Intel thread. Thank you!