So basically those guys just got a cheap piece of glass and wedged it in there. How is this a better option than a screen protector? The glass is going to have glare problems for sure, it isn't all that well installed and when something hits it even moderately (they did after all break several during the relatively simple installation) you are going to have glass bits in your car and in the on board monitor housing!

The only single reason I can think of that glass would be preferable to a screen protector is that it is optically clearer, but only slightly so.