It may sound like a good idea to load six rounds (one in the chamber), but they didn't do it. When not in actual combat, the rifle was carried empty. When it was loaded, it was loaded with a clip of 5 rounds and no one fooled around trying to load a sixth. Same when the rifle was shot empty. (Excuse me, Mr. Enemy, but don't shoot while I am fiddle-farting around trying to get an extra round in the chamber....". Bang!)
Some folks say controlled feed is to prevent jams. It may do that, but the original reason was to prevent an accident if the bolt is worked without being fully closed, leaving a live round in the chamber. If the bullet point of the next round strikes the primer of the chambered round, unpleasant things happen.
Jim