Woke up and could not get back to sleep.
Just another way to manufacture cases, not sure the reason. There are several headstamps, Ammoload, FM, IMT, and Maxxtech come to mind. Not all Maxxtech are stepped, I just saw one yesterday that was not stepped.
There are reasons not to use the stepped cases. They concentrate the stress at the step, and there are multiple photos on the web of cases that separated, particularly in blow-back action guns (like many of the carbines). The other is that the case wall can't be easily sized down low on the case. The case capacity may also be less, which would cause an increase in pressure if using load data for normal cases.