I don't know... the affected area on mine, IMO is not a high stress area at all. When I hold it by either set of handles there is no pulling on that area... the gusset area right beneath the zipper flange. If anything, that area sort of puckers up due to the slack that's created there from the handles pulling up the sides of the bag. Under no circumstances is that area ever pulled tightly that I can tell.
I have to pull the zipper flange aside to even see the area; it's just where the flange and the top edges on both the side compartments and the gussets all meet up. It just looks like sloppy edge coating due to a lot of complexity with different edges touching/meeting up to me, but it's totally concealed unless I go looking for it and it doesn't look like anything that will tear further if it's just left alone and not picked at.
All the stitching on mine is fine so far.
It becomes a high stress area when carrying crossbody- which is the way I use it most often. You're right - would not be a stress point with the shoulder straps.