Something I don't get about Spartan Ops...

More specifically, there’s something I don’t get about the mission “Shootout in Valhalla”…

Crimson was supposed to be extracted… so why send Pelicans in with Mantises on? Pelicans that could have extracted Crimson.

Did 343i dun goofed or is there something I am missing?

https://forums.halowaypoint.com/yaf_postst174560_Shootout-on-Valhalla-doesn-t-make-sense.aspx