Yes, it was Vince. But it's also an example of 'the bigger picture'. When it was sanctioned nobody thought to ask whether the new Mk2 Bren would fit into the chest. And the overhang meant that it didn't. Well, it did, after a fashion. The end of the chest had to be modified to create a shallow cam so that the gun body compressed the butt slide buffer in order that the gun would fit. If you have a chest without the chamfer to allow the overhanging butt plate to slide in, then it's probably a pre Mk2 gun chest.
I bet there's hundreds of Mk1 Bren nerds/fiends secretly checking to see whether their Bren chest is the correct one now. LISTEN...... THEY'RE ALL CORRECT.........!