John,
Maybe someone who's actually tried to get compensation for a Marathon tire will show up and comment.
I don't remember any recent comments in the last 2 or 3 years reporting first hand Marathon experience. Everything that comes to mind on Marathons seems to be old news, or a story about someone else's experience, and I don't remember any posts about submitting claims on Marathons.
The Marathon is listed along with the G614 and 2 other tires in Goodyear's RV brochure. So that might suggest equivalent treatment. But the written warranty for all of them has this exclusion: "Loss of time, inconvenience, loss of use of vehicle, incidental or consequential damage." So they could have a different policy for different tires.