@pithyrumble yes but that doesnt mean the actual action of adding at least 5 shipsets to everybodies account that has level 5 and one extra for all the people that have level 50 is something to be scoffed at.
The gathering of the data isnt what takes days upon days to do, not even for emmisary ledgers. its the act of unlocking the cosmetics that puts stress on the systems, dishing out thousands if not millions of those messages accross the several microservices is best done in smaller batches as to not put unnecesary stress on said systems. and that is why they give themselve a safety net by saying it can take upto 72 hours each and every time they have to dish out stuff to a large quantity of players (emmisary ledgers, twitch drops, corrections due to something going wrong with gold etc)
it basicly has nothing to do with knowing who is eligable but making sure the eligable people get their stuff whilst safeguarding systems.
so in this case the "knowing who is eligable" has been known since about the 27th, i mean that is an easy query of their database:
"Select * from Arena_RepTable Where Level equal to 50" & "Select * from Arena_RepTable Where Level greater or equal to 5"
hey presto all is known this puts 0 load on their systems, however the unlocking which started on the 10th of march means that they have to inject messages into their message queuing system for all records retreived from those queries i expect that the one for people of level 5 and greater would have at least a million records in it. then there is the fact that since this is a one off they probably have to send a unlock message for each shipset this means:
{number of people} * 5 = {Number of messages}, so for instance 1.000.000 * 5 = 5.000.000 (probably even more)
The act of sending those 5m messages is quite easy and done in maybe 30 minutes or so, however then it has to flow trough all their systems without risking deterioration of services and this number doesnt even take into regard the tens/hundreds of thousands that also had to receive the good boy.
having the 72 hour lead time is just a safety measure and most if not all will receive all their stuff well within that time frame and they communicate that time frime in order to not flood their support system with thousands and thousands of tickets of people complaining that they havent received the item quite yet.