It's perfectly obvious that when lifting heavy weights the muscles take the load rather than the spine, I posted such myself on this very forum just 2 weeks ago. As such, it's also clear that locking the core is a critical part of the setup for any big lift; whether it's done consciously or unconsciously, it must be done. As a self-taught older lifter, I find it beneficial to the 9's to consciously lock my core before a big deadlift or squat, in fact if I don't my lumbar takes a beating and I'm out the next day. All this about spinal position is hocus pocus, i.e. it's misdirection, since it could confuse lifters and lead to accidental injury. IMO the essential cues for both lifts (since they are in fact very similar movements) are; lock the core, head up, chest out, but most importantly, lock the core. Once the core is locked the spine will naturally be in the right position, which may differ from lifter to lifter or even lift to lift.