Your grade will be based on how much you learn relative to what you already knew . By signing this paper, you are agreeing that you are telling the truth and that if you are not telling the truth, you will be given an F for the course and agree to have disciplinary action taken against you by the university. So this person acts as both a mentor and a project manager. But be aware that the super experts will need to log as many hours as other group members. At the end of the term, group members will be evaluating each other as part of their grade, so fair effort by all will be recognized and enforced.
Value is to be gained by both the super experts and the others.
Mentorship is an important part of the tech cycle in Web development. But keep in mind that even the super expert will be expected to learn new material during the semester and will be graded accordingly. So make sure that you spend a fair amount of your time directing learning and a lesser amount of time doing actual tutoring. The goal is to have people learn new stuff on their own and have the total of the group be a diverse knowledge base. The remaining time should be spent by each member learning new things to them and unique to them.