I believe that the SteemMonsters account is where the packs go when they are sitting in players' Spinterlands accounts, as opposed to in their Hive accounts. once they are opened, they are sent to null. So the packs in the SteemMonsters accounts are for the most part unopened packs, in circulation. I don't know how many, if any, are owned by the SL team.
RE: How SPI made $10k+ from Splinterlands with no deck