MicrosoftDeletedPrograms like Word and Powerpoint do not use Pen as a primary input, and have had shapes as insert objects historically. This is different than OneNote, which is intended to be a replacement for a real notebook, something that is unique to Windows in the {Windows|MacOS|Linux} set of OS. Because of this, on Macs, Pen is not something that the OS supports as a primary input mechanism, and neither does OneNote, and like Word and Powerpoint shapes are inserted, not drawn.
As MS shifts to more unified code bases, the inclusion of a draw menu, using the mouse or touchpad was added. Perhaps Apple is even preparing hardware that will properly support drawing (or MS is sharing code on the iPad which already does).
But Inserting Shapes is consistent with the existing programs and hardware on MacOS, at the moment. And it is also equally valid to move it to drawing, now that it exists. But change should always be weighed.
