I want to understand what you are saying, it sounds interesting, but I'm not quite sure. Do you mean that things like the tools (guides, rulers, symmetry, etc.) help the user to know what a "correct" drawing looks like and that this will help train their eye/brain?
Yes, exactly. Not as a 'crutch', but more like training wheels. Thus, better drawing could maybe result faster
from using the program, than with pen/paper...?
SBP 'knows' what a line should look like, and provides a way to make an artistic gesture in the linework, that is possibly better than what the beginning artist could do alone. The artist 'wants' to make the correct/beautiful line, and SBP helps them succeed. This positive feedback loop is amplified with the guides and symmetry tools. The end result, when the tools are taken away, is that the artist is now 'better' rather than 'worse'. A crutch leads to atrophy...but training wheels lead to a new wonderful experience.
I have to agree with you. As someone who's just starting out with sketching, Sketchbook pro is a nice tool. I start my drawing with pencil on paper. From looking at the sketch, I can sort of feel where I went wrong but sketching proper line work as an overlay I can clearly see where I went wrong. For example for my last set of sketches, I realized that my idea of perspective isn't too bad but my lines aren't straight enough so everything looks off as the sketch progresses. It would be hard to get this kind of information without the tools. It's also quite motivating to end up with a corrected version of your drawing.