If you see the green you are aligned. If there is no green. where are you?
With irons you can see both front and rear and the way to alignment is clear.
Which is similar to any RDS-type sight. Use the rest of the handgun to index the sight - the silhouette of the frame, the side of the slide, etc. I have not used the Sig/Meprolight sight, but I suspect it's like a RDS that becoming accustomed to the sight includes learning to present the handgun already aligned.
I'm not convinced either, but I'm definitely interested and will be checking one out. One of my hopes is the sight, like a RDS, will reduce blurry irons without the gadgetry of a RDS.