Originally Posted by
mgilchrest
They are retracting their shoulder blades. Inwards and downwards towards the hip. It's very close to the squeezing of the chest upwards (note the effect in your reference video on the chest). It shortens the lever arm of the spine and gets the shoulders very close to the position they will be in at lockout.
It's effective albeit analogous to Rip's setup steps.
If I remember your deadlift videos from months back, you had no trouble setting your back in extension and rotating your chest upwards.