dynamic switching remains always on discrete

[rmottola]

I am unsure if it is a display bug or an oddity. MacBook mid 2010 Intel+nVidia with 10.13
If I switch to integrated, the menu reports Intel
If I switch to discrete, the menu reports nVidia

If I set dynamic, it reports and stays on nVidia. However checking in the Activity monitor no process reports "High performance graphics". Also staying on battery doesn't appear to incentivate the switch, even if Enery Preferences is set to "Automatic Switching".

When on dynamic and on battery, I still see:

Graphics/Displays:

    Intel HD Graphics:

      Chipset Model: Intel HD Graphics
      Type: GPU
      Bus: Built-In
      VRAM (Dynamic, Max): 288 MB
      Vendor: Intel
      Device ID: 0x0046
      Revision ID: 0x0012
      Automatic Graphics Switching: Supported
      gMux Version: 1.9.21

    NVIDIA GeForce GT 330M:

      Chipset Model: NVIDIA GeForce GT 330M
      Type: GPU
      Bus: PCIe
      PCIe Lane Width: x16
      VRAM (Dynamic, Max): 512 MB
      Vendor: NVIDIA (0x10de)
      Device ID: 0x0a29
      Revision ID: 0x00a2
      ROM Revision: 3560
      Automatic Graphics Switching: Supported
      gMux Version: 1.9.21
      Displays:
        Color LCD:
          Display Type: LCD
          Resolution: 1440 x 900 (Widescreen eXtended Graphics Array Plus)
          UI Looks like: 1440 x 900
          Framebuffer Depth: 24-Bit Color (ARGB8888)
          Main Display: Yes
          Mirror: Off
          Online: Yes
          Rotation: Supported
          Automatically Adjust Brightness: No