@null is also the account where "burned" tokens end up... which is why it will probably never exit the top 50 because tokens are burned all the time.
On Hive proper there's an automated mechanism that "sweeps" the burned Hive tokens from the @null account every minute or two so there's never a balance. Layer 2 (Hive-Engine) tokens are not swept so the account effectively holds HUGE balances of every Hive-Engine token ever issued that has burned tokens and continues to burn tokens. That's continue to build if/till the base code is modified.
=^..^=
sounds highly suspect
I do find myself wondering whether this constant clearing actually adjusts the total pool of Hive tokens on a "live" basis... or do they actually "go" somewhere.