Option to switch source/dest in prefs

I've noticed that it doesn't matter, if in prefs the tab-key is activated or deactivated - DO always switches between source/dest with tab-key. Is this a bug?

Not a bug. Tab always cycles through things, the option just restricts it to only the file displays, instead of e.g. file displays, search field and other elements.

I never switch between elements with Tab (except e.g. in forms), so I never noticed. Thanks for clarifying.