I agree with my colleague - this is often what happens, for several reasons. It may be just that when they check "approved" they are worried about additional inquiries.
It also may be that, for several possible reasons, a supervisor must sign off on the case before it is "officially" approved (so they may not be able to officially approve it yet).
My guess would be that everything is fine - give it longer than the one week (say, a month), but I would expect you would get an oath letter during that period.
I wouldn't lose too much sleep, yet. In my experience, this box is often checked, and simply allows the officer to avoid saying they plan to approve it, which can be true if they only want to review the file at the end of the day for completeness. Some don't like to say they are recommending the case for approval because it leads to more inquires, etc., sooner when the case isn't resolved promptly. Unless there is a substantive reason for your concern, I would sit tight, without worrying too much at this point. I'd expect an approval notice/oath within 30 days.