I prefer to think/believe, even, that the results of prior testing were favourable but maybe not perfect - so they tweaked, they have admitted that it is a two way street - they supply the cide, it is tested, results are studied by HQ and IMPROVEMENTS made - no use going to the FDA with some half baked cide!
The FDA doesn't give a blanket OK - they are very specific and so it goes - testing, improving, tweaking till they get it right. And don't forget the universaling side of things - including multiple ligands in the one cide to cover a plurality of variations be it flu or Ebola or HIV, etc.