It lets the shooter always have the high ground and provides better line of sight.
Seriously, I'm a big fan of the Unity riser, and it feels like something I've been missing all these years. While this does look ridiculously tall in comparison, I don't know what I don't know, and my experience with IR lasers can be measured in minutes. Having taken a class with these guys and seeing them shoot, I'm guessing that there's been some thought and experience into the design. Maybe it's like how Aaron Cowan described prioritizing primary sighting systems by omitting irons from his rifles. It might be for a dedicated NV rig where IR is primary, and the optic is the backup.