I would say that they need information from the i130 to make a decision if you are eligible for k3. That makes them review the i130, so seeing that with everything, you don't qualify for k3, they deny the k3. But since they already check i130 in the process, they just approve it instead of going through the same process when your priority date comes.
Also, I got to learn that petitions sent by mail are also scanned and put in a computer.