Windows 10 "Scroll inactive windows when I hover over them" not working on Dell XPS 13 9333 touchpad

So now that I have gotten the Windows 10 3-finger grestures to work on my Dell XPS 13 9333 (2014), it looks like one of the most useful features finally introduced in Windows 10 --the ability to scroll windows out of focus without having to click them first-- is not working with my touchpad, even though the option is clearly enabled in the Settings app.

Hower, it does work just right with a wireless Logitech mouse, in the exact same situation where the trackpad fails to work. Even more weird is that I have gotten it to work with the touchpad if the window in focus is one of the Modern/Metro apps, but it is just impossible to get it working with "normal" software.

I am running the latest version of the Synaptics Dell Touchpad driver (v.19.0.15.2), just installed from the Dell's website after uninstalling the previous version.

Anyone experiencing the same issue? Suggestions?

Thanks in advance,

-- Pol