Halo Online was shut down after beta tests in 2016, before this map and other bits of content could be added.
Last season, some armor from Halo Online was added to Halo 3.
The map itself isn’t too exotic, as far as Halo maps go.
I hope other Halo Online maps fly over to MCC too in future seasons.
It’s 2021 and I just played a new official Halo 3 map.