Dec 19
20
Google’s John Mueller was asked by Mihai Aperghis in a webmaster hangout at the 58 minute mark about a page Mihai 404ed but Google is showing as a 301 to a new URL, like Google canonicalized the 404 URL to the new URL.
Read more from the original source:
Google May Treat Some 404s As 301s & Canonicalize To A New URL