There are cases where backdating can be legal as long as you pay backdated as well. No idea if this is one of them, but the companies that do these things would know that it is being backdated and either they allow it or they don't. Maybe you should not be so quick to jump on someone and instead be dan lkaf zechus.
The only reason to backdate a surety bond is to prove coverage on a certain date or to file a claim. Spent enough time around surety bonds to know.
So maybe be dan lkaf zchus the other way that I (sometimes) know what I'm talking about. Unless someone can show me a scenario otherwise, dan lkaf zchus is a two way street.