Some time ago I modified the way board access is handled, so that it is possible to exclude people from boards, as well as separating board visibility from board access.
I also updated the UI in manage boards to cover this, but the reverse option - setting what boards a given group can see - has not yet been updated, mostly because I haven't figured out a nice way to display it given the way board hierarchy can be handled and thus you need the ability to provide indentation and stuff...
I also updated the UI in manage boards to cover this, but the reverse option - setting what boards a given group can see - has not yet been updated, mostly because I haven't figured out a nice way to display it given the way board hierarchy can be handled and thus you need the ability to provide indentation and stuff...