2.1.1302 Part 4 Section 126.96.36.199.4, spAutoFit (Shape AutoFit)
a. The standard states that if the spAutoFit element is omitted then noAutofit or auto-fit off is implied.
Office does not follow this and instead uses a hierarchy of text styles to determine if the text should be autofit or not.
b. The standard states that the spAutofit element specifies that text within a shape is scaled in order to contain all the text inside the bounds of the shape.
Office uses the spAutoFit element to specify that the containing shape should be resized to contain text.