One airline I worked for allocated work positions according to DOJ. We had about 6 crew bases at the time and seniority was based on DOJ regardless of base.
Other airlines, the SCCM would either allocate before the briefing, distributing the experience evenly or would just ask "who wants to work where?" and we just worked it out amongst ourselves. Our newbies had 'position cards' which recorded what positions they had worked previously and they needed to work all the positions a few times, including galley, so this had to be taken into account when the more senior crew chose where to work.
Assigning positions alphabetically was obviously thought up by someone who has never flown. I can't help but wonder if this is to demotivate senior crew so they will leave.