They would also be halving the bigger losers bigger loss though - so everyone is treated the same on their first month.
To be honest I do think the whole SOTW and SOTM thing is a bit daft and potentially demoralising, but that's a whole other discussion. Don't get me wrong, it's nice when you win it, but it's as much luck as anything else. Someone weighing 400lb who loses 4-5lb some weeks is no better a slimmer than someone weighing 200lb who loses 1lb consistently every week. They are both doing their best and following the plan.