This would rob future students, the university and the scientific community of the best possible professor and researcher for their money. To clarify this point, suppose the interviewers only really liked the mathematical model portion of the talk, or suppose the department only had the resources for mathematical modeling and not for biological studies. In this case, they would have hired Jack specifically for work he had no direct role in producing. The other issue raised by this case is proper recognition. Again, if explicit norms existed, problems would be less likely to occur.
Recognition requires both permission and citation.
Jack apparently had permission, since Bob helped him prepare for the talk and loaned Jack his slides. It is possible, however, that Bob was coerced into providing Jack with permission, in light of his vulnerable position as a graduate student in Hill's lab. One way of answering this question is to consider whether Bob would have been satisfied with Jack's acknowledgment slide if he had been in the audience during Jack's presentation. Added insight into this case can be gleaned by considering various paradigm cases. First, consider the level of Bob's permission.