When we bought a new pack for my wife in 2013, the (obviously experienced) gearhead steered her towards a Gregory pack and away from an Osprey, pointing out that her natural back curvature was not very dramatic.

Is this really a thing? I have noticed that Deuter and Gregory seem to have flatter harnesses than Osprey does. But I'm about to buy a new pack and haven't really noticed any discussion of this in my research.

My question is mostly does back curvature matter at all? I saw someone treat it as the primary consideration at one point, but I haven't seen it mentioned at all in my research.