As of Windows 10.0.28000.1251
Some keyboards do not associate the CapsLock and Shift keys together for all keystrokes; instead, pressing the CapsLock key defines an additional two shift states for specific keys. Therefore, some languages cannot by typed without the CapsLock key. The "SG" in the name orginiates from the first keyboard layout to use the functionality, the Swiss German keyboard layout.
0 out of 217 system layouts have SGCAPS keys, ordered below by the number of such keys.