If you are testing a drug with little in the way of a safety signal in combination with an approved therapy, then I very much doubt the FDA would ever try to second-guess you on efficacy in deciding on a Phase III. So in that context the FDA OK to proceed to a Phase III has little (if any) significance.
If the proposed trial is one-up against an approved therapy, then I could see the FDA showing more interest in whether there were plausible signs of efficacy.