Perhaps you're right, but only perhaps.
The manner of its growth from a 2 point difference all day to the gross error was slow at first but gained momentum after the 4.30 close...
But the 'feeling' here is that after the 4.30 close the Boards wend their own merry way occasionally due to the number of positions that have to be paid when the boards are equallised.
Boards also 'appear' to damp down Eliot waves for similar reasons.
Are you talking about a difference between an SB quote and the adjusted future? They could get away with moving the goalposts slightly, but not by 20pt, and I doubt very much it would be anything to do with equalising the boards (whatever that is).
You'll have to explain the Elliot wave bit, as there never seems to be any agreement when identifying EWs, let alone see when they're being 'damped down'.