The thing I will say about spining is, I do it. Every shaft, every time. Even when I pull a shaft to reuse in a different head, I will re-spine it, just for the hell of it.
I have a new Epic Flash driver head, and also a new Cobra F9 head. I was shocked when I weighed the EF head at 204 gr.(with adapter), but was nearly floored with the F9 when it came in at 206 gr.(with adapter)! My 1st thought was about how the shafts worked when people would dick around with all the settings. Contrary to popular beliefs, those shafts are not aftermarket, they are the OEM 'needs'. Even with the mfr. brand name on them, they can be squirrely, at different settings. Imagine getting one of those 'wobblers' in a head that weighs that much, and at the 'new normal' lengths of today!? Normally, I will just discard a shaft that comes in a driver, knowing(in my mind) it's almost worthless for me, with the 'supposed' flex on the label, or the weight it's 'supposed' to be. I'll use a shaft that I know the correct weight of, and the flex to be of my needs. And, I spine the shaft and then put it with the setting I want. And leave it. If I then have a squirrely shot, well......I know what's to blame. Or who.
Bad swing mechanics, or perfect swing mechanics....you still need every bit of help you can possibly have. Golf is sheer fuckery. Nothing less than. Take the help available!