Cannot make a key binding for Shift+Enter (normalModeKeyBindingsNonRecursive)

Describe the bug

I'm trying to remap <Enter> and <Shift>+<Enter> to create new lines in Vim normal mode.

<Enter> works as intended, but <Shift>+<Enter> doesn't work. Here's the relevant setting.json:

    "vim.normalModeKeyBindingsNonRecursive": [
      {
          "before": ["<Enter>"],
          "commands": ["editor.action.insertLineAfter"]
      },
      {
        "before": ["<Shift>", "<Enter>"],
        "commands": ["editor.action.insertLineBefore"]
      }
    ],

I've tried other strings like <S-CR>, which don't work either. What am I missing?

(I've also disabled all Keyboard Shortcuts that use shift+enter.)

Environment (please complete the following information):

• Extension (VsCodeVim) version: 1.16.0
• VSCode version: 1.47.3
• OS: macOS 10.15.6

Start by reproducing the setting.json configuration using vim.normalModeKeyBindingsNonRecursive in VSCodeVim, with the and + mappings shown. Trace the keybinding entry point and compare the handling of these sequences; done means Shift+Enter invokes editor.action.insertLineBefore while Enter continues to invoke editor.action.insertLineAfter.