Well, the subject matter is stated in the instructions for the Lee Pro Auto-Disk Measure. Specifically, it says "Do not use for black powder. Black powder is an explosive".
My conclusion is that the instructions say this because they want to avoid a situation where people think that loading any kind of black powder in any kind of cartridge is okay. Clearly, there are many of us who load cartridges with black powder as appropriate. There isn't a logical reason why a Lee Pro Auto-Disk Powder Measure is incapable of metering the correct charge for a BP cartridge.
My conclusion is that the instructions say this because they want to avoid a situation where people think that loading any kind of black powder in any kind of cartridge is okay. Clearly, there are many of us who load cartridges with black powder as appropriate. There isn't a logical reason why a Lee Pro Auto-Disk Powder Measure is incapable of metering the correct charge for a BP cartridge.