Shift is universally used to constrain a drawn art to 0-45-90° angles when using a tool. This applies to lines, rectangles, other shapes, anything that can be clearly oriented.

The Dimension tool breaks the paradigm — we can’t hold shift to constraint the angle of the drawn dimension line when creating radii or dimeters.

Some standards require us to have these lines too use integer steps, like 15° or 30°... this is very hard to comply now.

Please either make the tool to respect angles set in Preferences > Smart Guides, or make it a separate setting in the tool’s options.