Have a file test.txt:

function a() {
    var a = {
        x: 3
    };
}

Use the following settings in the user settings and make sure there are no workspace settings:

{
    "editor.renderWhitespace": true
    , "files.autoSave": "afterDelay"
    , "editor.tabSize": 4
    , "editor.insertSpaces": false
    , "files.trimTrailingWhitespace": false 
}

Open the file and the user settings side-by-side:

Go in test.txt and press a Tab. It is ok, it inserts a tab character:

Go to the settings and change "editor.insertSpaces": true.

Go back to the file and press another Tab. Observe, it still inserts tabs.

This used to work.

The editor status contribution should change editor options only if there was a manual user interaction with the tab status for the file