this particular optimisation became possible thanks to changes in 4.19.
I observed that the allocation of Event objects and calling ->call() was costing us a significant percentage of the time taken in PlayerAuthInputPacket handlers. This change produces a measurable 2 microsecond reduction in overhead for PlayerAuthInputPacket handling when players are not moving (10.7 -> 8.7 microseconds). On a server with 200 players, this translates into a 1% reduction in CPU load for PlayerAuthInputPacket alone. It will also benefit other packets, but not to the extent that PlayerAuthInputPacket benefits.