Good lifts!
In my opinion, many...if not most of the 'correct' ways to do an exercise are wrong.
Biomechanically, there are so many leverage points, and joint angles...especially in a multi-joint movement like the deadlift that a generalized 'form' instruction of "keep your head up" is really pointless.
Unless you're willing to measure the shearing forces, fulcrum, joint angle, distance from the midline of the body, etc., etc. for each vertebrae (taking into consideration a person's natural predisposition to kyphosis or lordosis at each section of the spine), also taking into consideration the hip, knee, shoulder, elbow and wrist joints....and doing this for EACH person doing the lift, you can't really be certain of a correct form.