I saw a MYOGer on Reddit say that in his opinion, Ultra must be seam taped because the outer UHMW fabric has some degree of stretch, but the mylar film backing has nearly zero. Because of this, over time, Ultra’s mylar backer is prone to seam and panel delamination or pin-holing as seen in the pic Nunutak links above. This is the first real world proof I’ve seen of his comment, but appears to hold true on n=1 sample.
The seams make sense – a natural stress point, but that problem can be taped away. The mid-panel delamination is more concerning to me, as there isnt much you can do to reduce stress in the middle of a backpack panel over time.
Regardless, I think I’ll end up with a Kakwa 55 for my next pack, but will tape the seams immediately with DCF tape (or whatever is recommended for Ultra. Same stuff?) not for waterproofness, but for mylar delamination prevention.
As for the OP question, does an Osprey pack not meet the durability threshold? I had a Kestrel 68 as a starter pack and although it was relatively heavy, it was pretty bomber. Everyone seems to love SWD too, but cant comment on them personally.