What you should say is that kind of speed might be abnormal for you because you can only talk about the limitations you place on yourself as I can only talk about the limitations I place on myself. However the limitations I would place on myself would be greater on that kind of road on a rigid bike vs one with suspension.

And let me be clear, the entire road that I am talking about (as well as many others in Colorado and the Mountain West) isn't littered with baby heads and rain ruts. Much of the road is relatively smooth...although rougher than you'll find in your neck of the woods...with some rough patches. There are enough rough patches to make suspension worth using. If I were stuck with using a rigid touring bike, I'd pick from many alternatives to the route that I'm describing. I'd miss some of the history, most of the challenge and much of the pain of the route I'm describing but the alternatives would be better for a rigid road style touring bike.

I do use a rigid road touring bike for most of my touring. But I do so on a road (mostly) because I've found them very limited for more adventure style touring. Alternatively, I wouldn't use a mountain bike for mostly paved touring. But there are times when I like to get off the pavement and find some of the less traveled routes and a mountain bike is the right tool for that job. I suspect that prodgers is thinking about as well.