Can this be because it's not a laptop bag? It's not listed on the REI site as a laptop bag. I believe it may only be a hydration backpack that fits a laptop rather than a bag with a laptop sleeve.

Just an FYI, key features of a laptop bag is for the laptop not to fall out if the zipper is unzipped or starts to unzip while on your back. Though not designed for biking, you should look at the design features built into Tom Bihn, Booq and Brenthaven backpacks. The last thing you want is for your precious laptop to hit the ground because the zipper gave out or you forgot to close it completely.