I didn't press them too hard on it, mostly because I was already leaning so heavily towards the Unaweep pack. They sound pretty confident in the zipper, and compression straps wouldn't really work with the pocket setup. I'm going to assume it was a combination of saving weight and commitment to the center-zip design. I'm no pack design expert, but I would've though a zipper running along the size of the pack would be a better choice, where the compression straps could take some of the stress.
MR packs seem overbuilt to a degree that most backpackers don't want and probably don't need, so I guess this new line of packs reflects a willingness to sacrifice some durability for weight savings.
