Thicken works to the outside, inside, or split.
Extrudes can be extruded in both directions in options.
Why can we not create ribs in both directions within one feature?
Use-case: 3D printing does not require drafts and enclosed volumes still require ribs for reducing material while maintaining strength.
Simple example: Create a rib in an I-Beam where you have two plates that need to be connected with ribs.
I know the Rib feature was created for injection molding but plastics manufacturing has gone far beyond traditional capabilities.