I feel like this test as a whole is not only for the b-rank but also the actual a-ranker who is going on the away mission.
The first phase the a-ranker having to give merits/demerits double as them having to spot and cover for the weaker link of their team
The combat phase is to trained them for the neighborhood, obviously being outnumber by both the b rank but also trion soldier that's not the standard model since every country in the neighborhood would have very different variant to serve different purpose and combat doctrine.
The same can be said for the b-rank with them having to deal with a-rank customize trigger that's not going to be the standard border trigger, especially tamakoma 1st. The special event obviously going to be jin and amo carrying BT as the wild card and I have this feeling that they are going to be a wild card going against both b-rank and a-rank