To put all that has been said about your excessive side tilt in perspective, it helps to examine what a "conventional" windup from a "conventional" set up is in its basic form.
Conventionally, there's a bend at the waist at setup. Into the windup, there's substantial loss of bend at the waist which turns into substantial bend in the left side. The reverse happens in the downswing. This change in bend keeps the spine from dramatically swiveling (swiveling like a rotating bent rod).
If you pre-twist with a conventional amount of bend at the waist, you have not much choice but to swivel your bent over body back to impact to face the ball and make all the necessary compensations to effectively strike the ball. There's an irony here in that the concept of a pre-twist (along with a few of the other "biomechanically efficient and simpler" pointers) may actually introduce complications to the swing.