You can reach IsTabStop=False controls using the arrow keys?

A number of controls on my form have IsTabStop set to False. As expected I cannot set the focus on these controls using the TAB key. But in this situation setting the focus can still be done using the arrow keys. Is this by design or perhaps a standard feature of Windows?

I can't completely rule out OpenDCL code as the culprit, but I sure can't find anywhere that OpenDCL is causing this.