As of version 20.1 - 0.4-v2, for fabric, if you have keep inventory enabled and die, you keep a copy of the backpack you were wearing in your inventory but the backpack with the items inside stays in your death spot.
I believe the correct behaviour should be that the backpack would be kept in its dedicated slot with the items inside it and should not be dropped on the death spot.
As of version 20.1 - 0.4-v2, for fabric, if you have keep inventory enabled and die, you keep a copy of the backpack you were wearing in your inventory but the backpack with the items inside stays in your death spot.
I believe the correct behaviour should be that the backpack would be kept in its dedicated slot with the items inside it and should not be dropped on the death spot.