As with all SW development, there are always a lot of things that they "could have" or "should have" but every day you wait with malware which has a know patch

As with all SW development, there are always a lot of things that they "could have" or "should have" but every day you wait with malware which has a know patch out means less spread for you. So they probably made the decision to just get it out as quickly as possible even if it was not perfect.