YEA! Luc is a good dog.

A friend of mine adopted a very young (6 months perhaps) Miniature Schnauzer because the two previous owners could not deal with her pooping in the house.
My friend was good with the dog, but even so it took the dog a while to catch on (Maybe a year) The dog could hold it for what seemed like very long periods of time. When she got walked, she was picky about where and when she went. (I think my friend eventually taught her to go at a certain spot during their walk.)
The dog sometimes would go near the pads from the pet store -- she would miss the pad by a few inches and so on.

My friend was patient and the dog eventually caught on about where she is supposed to go -- although she still can hold her poop for longish periods of time (more than a day or even two if I recall.)

I know you have experience with your other two dogs but perhaps SOMETIMES this is a Schnauzer trait.

M.