I picked up my T-bird Storm on July 10th of this year and have already complained and received replacement bags. After talking to the dealer and rep the bags are made without the stitching on the inside hinged portion of the bag. It was designed and made that way. My replacements are better but will eventually begin to collapse or cave in on the top as the first set did. My solution, that I have not tried yet is to unmount them and get some Marine glue, a soft towel, wooden blocks and a few clamps. Gluing the interior moulded plastic stiffener to the stitched (not real but composite leather) seam. The other option of course is if you have purchase the bags with the bike the service warranty should cover replacements. I took photos sent them to my dealer and they forwarded them on to the local rep who approved replacements, which I received in about a week. ~ for what it's worth.
Just talked with my dealer and confirmed what you said; that's just the way they are made but they didn'nt have an answer as to why. I am going to contact Triumph corporate and see if they can provide an answer. Your solution to a 'self fix' is exactly what I was going to do with mine but it's a shame to spend all that money and have to spend time making things better. Thanks for the response and info.