It is not uncommon to hear of stories where designers and design professors bribe their employers for a position here in Asia. The give and take of the design employment world is not what it was 10 years ago. Your story exemplifies and adds to this new reality.
Kick backs, bribes, extortions and the generalized over reaching of ethical boundaries is the new normal unfortunately. It is making it difficult to operate with a high degree of integrity as many cannot afford to pay the price of admission and are forced to capitulate.
I think what they are really after is measuring how your work generates synergy with their design group. How do your ideas mesh with theirs and how do you fit into the dialogue of a project and its impact on the team. You can turn this around on them. Look at this opportunity to get to know each one of the team members through your work. Use this project to interview them and see if your ideas spark the kind of synergy that you could work with if you decide to accept their offer. Use your project to measure their potential and their worth as you discuss the nuances of the project in your final interview.