Single-rail power supplies do not come with the over current protection (OCP) safety function on their +12V rail. OCP limits the current that can go through the PSU's rails into your PC when it exceeds a certain point, called the OCP set point. OCP is necessary because if you experience a short circuit in your system (which is unfortunately possible, even with modern equipment and building techniques) OCP will cause the power supply to shut off, preventing excessive levels of current from flowing into your system and damaging the hardware attached to it.
A single-rail power supply unfortunately does not provide this safety feature, due to its high current rails with up to 100A (100A x 12V = 1200 watts!). In the event of a short circuit or other failure of hardware, current flows unhindered into the system and damages everything in its path. If the user is unlucky and acts as grounding at that exact moment it could be even life-threatening. Are you really sure you want to install an unsafe power supply like this?
At Antec we deliver only high-quality power supplies and always make sure our customers are safe and can enjoy the hardware components they’ve purchased. So every multi-rail power supply we offer comes with the OCP safety function standard.