You linked a thread from 2008. You think these guys haven't learned anything in 8 years? If the most recent version of the book doesn't say it, it's probably not important.
Additionally, you should evaluate it on your own and ask questions from there. You said Simma Park teaches it without the shrug and you think it works better. Why might that be so? By what mechanism would a shrug in the squat be beneficial or detrimental?