They did tell the reason. They are removing an extra 301 from the chain, which means faster response. Most desk tops this won't make a difference but on mobile networks the round trip for the extra 301 can add a second to target site opening up. Probably with a different domain they are (or are planning to) move to a wider distribution of redirection servers geographically). A destination page loading up may not be an "experience" but having it take too long to load on mobile is a "bad experience."