I don't know about the rear window. If the oem glass is special, such as having a "solar tint" or something like that, it might be best to specify oem glass. It will surely cost more.
We get lots of rock damage here in New Mexico. I had several repairs on my 2015 Volt, and then got a big chip right near the edge of the glass. I went to SafeLite. They said it couldn't be repaired, needed to be replaced. Apparently all their glass is cheap china-made. The Chevy dealer quoted me around $600 just for the oem glass, and then I would have to pay the labor for installation, which would be farmed out to a local glass shop, since the dealers don't do glass. I ended up getting a good enough repair on that edge crack; it lasted two years until I traded the car on my 2018 Volt (which got a rock crack within its first two weeks on the road!!)
I want oem glass because the Volt uses "special" glass that helps the car maintain cabin temps and (I assume) filter out at least some UV. I doubt that the $200 jobs use very good glass.