If you fill the tires equally within their recommended range and then load the back more heavily, the rear contact patch will be larger than the front which will affect handling and could contribute to a dangerous front wheel slideout on a wet corner. Granted the difference wouldn't be huge but when you are pushing your luck on a wet downhill corner, every little bit helps.
No doubt I'm an old fuddy-duddy who's a chicken, but I really, really try not to do such things when touring. I'll admit some of that's based on experience, when I was stupid going downhill from Haysi, VA, around a corner in the rain. When I got the bike under control, I was fully aware of the traffic density, housing density, and distance to a medical facility. Since then, I've tried to take the downhills easy enough that I felt like I could slow or stop well before I was in the danger zone. At least while touring.