The coach thinks those guys are incredibly talented noob pitchers. Since they are noobs, he needs them to get real game experience.
That match exactly is that. It's even better that they are exhausted from the camp. The coach can see for himself how they behave at their limits in a top-tier game.
Remember that their team lacks a monster pitcher. Tanba is top-tier, but he can last a season alone and isn't in the monster class.
Seidou is extremely lucky to get two probable monster pitchers. But they need to have them grow fast, Sawamura being the MC, he's the one that should outgrow everyone, with Furuya being a catalyst, Miyuki and Chris giving guidance.