hi barretts, been a long time it seems, dont see your name up here much anymore.
Having ridden a lot on my 26x2in 50mm supremes, I personally had the opposite opinion than yours. I found they rolled well, and at the right pressure did a great job at absorbing bumps and stuff.
This year I went on a ride with a friend, me on my touring bike with the supremes, and him on his 700x32 conti touring plus or whatever they are. We both had one pannier on, but he weighs probably 80lbs more than me, and I was surprised how on a shallow downhill I distanced him when we did a "no pedal" simple test, probably starting at less than 15kph, no real head wind to speak of, and probably getting to maybe 30kph tops. I know there are other factors like hubs and how smooth they are, but I do think the bumps on the bike path played a part, and also the slickish supremes also was a factor.
Ive also noticed this when touring with similar loaded riders, that I am at least equal if not faster on downhills than others with my 50mm (mine measure also to 45mm) compared to them on either narrow tires and or much heavier riders.