So they have good compatibility, why does that mean THEY MUST form a team? It doesn't explain why they can't both just say no - why does the guild have the right to revoke their licenses if they do so?
adventure guild is a company, they probably have to sign a contract/agree to follow certain orders to officially work for it, so it's just saying if they break contract/don't follow higher ups' orders, they are fired.
note: most companies worldwide
are allowed to this, but an immediate ultimatum when they both don't want to (and have no other issues , as far as we know), is usually from a less reputable company