Sounds like a bit of confusion there on Harris' part...
Greg Allman was an Executive Producer on the film, not a line producer. He was involved in the financing and budgets and probably had a contract which included a clause on creative control ( as many will when the film is about them ).
An executive producer (EP) enables the making of a commercial entertainment product. They may be concerned with management accounting and/or with associated legal issues (like copyrights or royalties). An EP generally contributes to the film's budget and may or may not work on set.
In Motion Pictures, an executive producer oversees the filmmaking with regard to film finance. They liaise with the line producer and report to production companies and distributors.
In Television, an executive producer often supervises the creative content as well as the financial aspects of a production.
A line producer is a type of film producer that functions as the key manager during the daily operations of a feature film, television film or the episode of a TV program. A line producer works on one film at a time. He or she is accountable for human resources and all kinds of problems possibly occurring during the making.[2http://en.wikipedia.org/wiki/Line_producer