From Halopedia, the Halo wiki
|SHIP NAME: UNSC PILLAR OF AUTUMN
Not terribly surprised at this selection due the over-bulked, overmassed honeycomb interstitial framework. It’s ironic, I suppose, that the same absurd design that forced this ship into the scrap yard years ago is resurrecting it for RED FLAG.
A cruiser was an obvious choice, as noted in my prelim, but the reason she opted for a Halcyon - this particular Halcyon, in fact – is because it can take an incredible beating without suffering functional compromise far longer than any other ships we current field.
She might be slow and cumbersome, but she’s a real beast, especially now that they’ve tweaked her armament. Good choice.