Rear Hatch Glass Replacement Option?

I’ve Never Seen This Hatch Glass Before

The rear glass hatch of this van has been replaced with a plastic type window.  The plastic replacement isn’t flush in the hole.  The window is set back about an inch or more outward.  At first glance it isn’t very noticeable.  Once you do notice it, it stands out quite well.

What might the purpose of this?  There isn’t a major gain in space because of it.  Perhaps the molding process makes it easier to make?  Perhaps it is to make it stronger being it is plastic?

Whatever the reason, and whatever company made it, it looks cool.