The answer is very simple. Incorruptibility has never been regarded officially as a miracle within the Catholic Church. There are many natural processes, and several man-made embalming techniques, that can cause a body to be preserved. Otzi, the 5000 year old “ice man” would technically be considered incorruptible, but that’s because he was buried in a glacier and preserved. Many Catholic saints have uncorrupted bodies, but they were embalmed. The Catholic Church does investigate incorruptibility, but in a way in which it sort of announces the information, and lets the faithful decide how to interpret what’s found. It may be a sign from God, or it might not.