Based on your location, and the other production dates. Here's a theory...
They start production on new 'lines' starting with those on the Eastern half of the country and then working west.
I'm in Wisconsin, and my S75 started production on 2/28.
@bigred79 is in CA, and his entered production on 2/27.
From the order status thread, I hadn't seen anyone from the West coast enter production until the first and second week of March.
So I'm guessing if you're the end of one 'line' with the old MCU, and I'm near the start of the new 'line' with the new MCU. Again, this is all speculation, as I don't pick mine up until 3/24.