As usual, the announcement was posted on Halo's official Twitter account, you can find the official post below. In summary, and for non-English speakers, the Covid hasn't spared the team, and the studio wants to make sure that the game lives up to expectations.
This is perhaps a bad for a good, since the last video of the game was far from unanimous, both in terms of graphics and gameplay. Better a good late game than a bad game.
Original content by Robin "Raiden" Bouquet.