Not in dconf but I found it in MateConfig Configuration Editor 1.2.0 - apps / marco / general, set as you describe. focus-new-windws help says...
"It has two possible values; "smart" applies the user's normal focus mode, and "strict" results in windows started from a terminal not being given focus."
Sounds to me as if it may only refer to terminal launch? If it's more general then I now need to find "this" user's "normal focus mode" :(
I suspect it's in some schema somewhere but there are rather a lot of quite complex ones to work through. Another day.
I have three config editors, all a bit different and all claiming to edit my entire set of configs. None of them does and they sometimes do not agree with each other; or one will alter a setting where another fails. :(
I found a schema that may apply in gconf schemas / metacity / general...
...but I have no obvious folder /shemas - I assume it's actually a sub-folder of something else; I'll have a deeper look.
Thanks for looking, anyway. :)