System Information
Operating system: Ubuntu 18.04.3 LTS (Bionic Beaver)
Graphics card: NVIDIA Corporation GP107M [GeForce GTX 1050 Mobile] (rev a1)

Blender Version
Broken: blender-2.81-ed779333bb82 to current
Worked: blender 2.80 release version

Short description of error
When using the "Position" output from the "Geometry" node for textures the "Bump" node does not output a normal map based on the bump map.
This "Position" output also doesn't work with the "Displacement" node.

Exact steps for others to reproduce the error

1. Select cube.
2. go to the "Shader Editor".
3. delete "Principled BSDF" node.
4. Add a "Geometry" node.
5. Add a "Noise Texture"
6. Connect the "Position" output of the "Geometry" node into the "Vector" input of the "Noise Texture" node
7. Add a "Bump" node.
8. Connect the "Fac" output of the "Noise Texture" node into the "Height" input of the "Bump" Node.
9. Connect the "Normal" output of the "Bump" node into the "Surface" input of the "Material Output" Node.

Edit: You can switch out the Bump node for a "Displacement" node and there will be no bumps displacement texture.