Under Group Single only one life is insured. Group here means an institution with a potential number of lives that may be insured. Note that not all of the members in the group will opt for a policy. For example, of all the JetPrivilege members, not all would opt for a HDFC Life policy.
Even though it might look that there is a “guaranteed” premium without renewal issues, there still maybe renewal required (from the persons who wants their life insured again). If I go for a term cover this year, next year I might choose not to insure again. Further it might not be as sticky as you might think. Our organisation had tie up with LIC for group term cover for us two years back. Last year, we went with PNB Metlife. This year it is ICICI Pru Life. 
Thus our lives were insured every year but not with the same insurer!
I’m not sure about the “highly negotiated policies” or what monetary benefit is there for the group. In our case the premium had only gone up on renewal this year. HDFC Life pays some commission for every policy sold through JetPrivilege.