From the M4 Manual: "NOTE: the gun must be loaded with the hammer cocked so that the carrier latch can retain the cartridges as they are inserted in the magazine."
The Benelli M series uses a unique cartridge loading action. All the details of "why" it is that way is not explained in the manual. However, watching the action indicates that in order to keep the complexities of the interoperability simple (i.e., increase reliability) and allow tactical flexibility of operations, Benelli designed it that way.
In the below videos observe the relationship of the cartridge drop lever and the cartridge latch when the hammer is cocked versus fired position. Yes, a little complex but it appears the design interoperability is part of the drop/ impact induced firing safety system.
Another operation that is allowed with the way Benelli designed the loading interoperability is to support the Combat Reload (i.e., loading with the bolt forward and a round chambered) supporting topping off the magazine (tactical reload), changing out or adding mixed rounds (shot vs slug vs 2 3/4" vs 3") and malfunction operations. After watching the below videos, as a mental drill, visualize a combat load operation as to the relationship of all the moving parts. ?
These two videos show the actions in motion and will let you see how the shell lifter works with respect to the hammer.