Never said anything about any "wives tales" or rear tire failure causing a crash. The vast majority of rear tire loss of air that I've experienced/heard/read about did not result in any crash but just an immediate need to pull over and take care of it, regardless what tire was back there. Had this happen to me personally. So naturally you won't hear of any c/t on the rear causing a crash since the c/t is obviously less likely to fail on a mc than an mc tire. Not saying a rear mc tire fail won't cause a crash, just not so common. Also, you will naturally find numerous listings of mc tire fails causing a crash since if there is a c/t on the rear and the front mc tire fails resulting in a crash it would be reported as a mc tire failure cause. Anyway, my only point is that mc tires are engineered to work together front and rear and the front will likely wear faster, I didn't say it would guaranteed fail, with a c/t on the rear. There may possibly also be odd tire wear patterns on the front in this case. I consider cupping an odd tire wear pattern that should be resolved with some form of adjustments to pressure, front steering bearings, alignment, etc. Again, IF the front tire fails as a result it would be reported as a mc tire failure. It would also be an indication that the rider might not be paying (enough) attention to his/her tire wear (obviously you do pay attention to it). Obvious instances of road hazards excluded there. Another thing... whenever I have heard of a tire of any kind popping off the rim (mc, car, truck, etc) it's not about the bead coming outside the rim, which I know is really a tight fit and unlikely especially with a c/t, but rather the bead falling to the INSIDE toward the center of the rim, which is easy with any tire with no air pressure to hold it out. If this happens and travel on that tire continues very far it may possibly be worked outside the rim after the fact due to side forces and extreme weight of the vehicle on a flat tire. So that argument is moot. I know that run-flat tires don't normally have this issue if at all since they are designed to hold up the vehicle weight without air pressure.
I cannot explain why you don't get the miles on mc tires that I do. I'm not an aggressive rider, but it sounds like you aren't either. You do tend to load your bikes more during LD riding but I would expect that would affect the rear more than the front. Only possibility I can think of might be an issue would be the cargo carrier putting significant weight behind the rear tire causing the front tire to be lighter on the road than normal. But then you would likely notice that in steering control right away so maybe not. I've never used a cargo carrier, but I have pulled trailers/campers with my GW and my ST. Those would present very different dynamics on handling and weight distribution, and tire wear, compared with a cargo carrier. Trailers only put 20-30lbs vertical weight within 12 inches of the rear tire. A cargo carrier would place more vertical weight farther behind the rear tire.
It's a trade off in the end. I know of many riders who use c/t on the rear of many different bikes. As long as the rider is watching the tire wear and air pressures all around it's up to the individual what they want their bike to have on the rims. I'd personally prefer to stay with buying 2 sets of mc tires in 35000 miles than buying one c/t and 5 front mc tires in that same miles. Of course this depends on how these tires wear for me.