Interesting question. I have only crossed water with under 10" depth, but with claims from FCA and photos posted by other, I know I should be able to cross deeper waterways.
Regarding the seal on the rear door .. I am wondering if you saw the "splash" due to the loose fit of the inner weatherseal? I know that mine has been knocked out of place a few times when a passengers exit on the driver's side. I would see it sticking out of the the closed door and have to put it back into its proper location. Seems like a good fit, but occasionally it falls. One time I found the seal laying on the ground under my Jeep. I brought this to my dealer back when having one of the original TSBs done and they said it was an anomaly but would look at it. It stayed in place for a few months before starting to fall again.
So, to your question of failure claim, if I experienced water intrusion in the rear, I would totally be suspicious of that seal and see the failure as a design flaw, until proven otherwise.
2014 Jeep Cherokee LATITUDE 4X4
3.2-Liter V6 24-Valve VVT Engine
9-Speed Transmission With Jeep Active Drive II
Cold Weather Group
1st Jeep '74 J-20 that spent it's first life as a tow truck - RIP