The canon is anything that appears in the games. There are clear timelines between many of the games, asserted within the game text or game subtext.
Producers have gone on record echoing what's states in the HH, both before and after it was published.
Do not mistake the canon for something the producers and designers feel in any way bound by. That's not what the term means when discussing media.
We could less-figuratively use O'Leary as the signal fires of Gondor.