This is correct. Cervical hyperextension is not recommended; doing it before the lift might help give the lifter a better sense for the position of 'chest up, lower back tight/arched', but the hyperextension (e.g., looking at the ceiling) should not be maintained during the exercise itself.
This is, by the way, one of the technique mistakes Cressey speaks of in a recent article
without reference, however, to squatting.
Rippetoe and Kilgore, Starting Strength, 2nd edn, go into this at length: looking at the ceiling "is the enemy of correct bottom position, hip drive out of the bottom, and correct chest position".
Returning to the OP's problem, if he can learn to maintain correct positioning, then (to add another quotation): "Don't be afraid to lean over, stick your butt back, and shove your knees out" (i.e., don't let them draw together).