Only when observing south one *could* correct in declination with that motor.
Quite - it only corrects in Dec around the meridian. But even for astrophotography, that's where you tend to image (at least with Dobs - no mirror flop).
If you autoguide one of Tom O.'s dual axis platforms, BTW, given that autoguiding is using a feedback loop, the guiding software can still work even if its two corrective axes aren't perpendicular, though it becomes very hard, of course, close to the Western and Eastern horizon.