Tools.viewTool not working?

I'm trying to find a way to detect when you're in the Flythrough mode (when you hold the right click in scene view) and looking through the scripting API I found https://docs.unity3d.com/ScriptReference/Tools-viewTool.html

Which if I'm understanding correctly should return ViewTool.FPS when in Flythrough mode.

However, I scripted a simple test script to query this value but it is only ever reporting ViewTool.Pan no matter what view tool I'm using

Is this a bug or am I using it wrong?

in Unity 2019.1.8