But you should think I might fudge it!
The very fact that I value a method because it prevents me from fudging tells you that I might very well fudge a DC if given a chance.
I have in the past, in a couple different ways. When I kept the DC private from my players, and they rolled close but not quite to it, sometimes I nudged it downward so they'd succeed. Sometimes I wouldn't bother setting a DC, and just let the players succeed if they "rolled high." Why? I was too much of a cheerleader fit the players, maybe, or I was too invested in making sure the plot moved forward.
So, yeah, I need a method that curtails my opportunity to fudge the DC. And that's why I don't want the players rolling the dice before I tell them to.