That really big angle causes the advance to be more for a given increase in rpm. The '68 Auto and Manual have very similar advance rates, so that something else that doesn't seem right (edit: or I should say different) about the NOS shaft assembly. I think its for something that needs a quick advance all the way to the top. Also taking a closer look at the primary springs in the photo the one is heavier and less coils, so the start would be at a higher rpm.

Graphed the two advance curves. The primary springs were probably the same, the automatic had a secondary spring with a little shorter loop and/or the adjustment tab was a little further out compared to the manual.

Installed on their respective engines at the spec base timing ( 0 for manual, 5 BTDC for auto) they provide very similar mechanical advance curve.