The .9 stub is a gold nib. It has line variation, but the corners are rounded. It isn't crisp, or edged, so it less particular about the angle it is held at.
Hmmm ... Having looked around, the only 0.9 mm "italic" nib by Stipula I can find is a steel nib. If you have a source for gold Stipula 0.9 mm stub or italic nibs, would you please share it?
ASAIK, there is no clear distinction between crisp and cursive italic nor between cursive italic and stub. It appears to be a continuous variable in shoulder roundness and in line differentiation. If this is incorrect, please educate me.