"Cook" seems a little too high for steel-cut oats and in any case doesn't last very long, whereas "warm" seems like it would never cook the oats at all.
I ran the cooker through a couple of cycles in "cook" and feel the consistency of the oats is a little less smooth and creamy than I get from my overnight crock-pot recipe. The crock-pot recipe produces excellent results. And having to run the cooker repeatedly, adding water to the steam heater (not the oats) each time, is more attention-intensive than using the crock-pot, which really is a "set it up and leave it alone for six hours" kind of process.
Both the rice cooker method and the crock-pot method result in pots with some pretty seriously stuck-on oats.
More experimentation is required, I think.