My two cents worth:
That book is a little dated now. I think it was published sometime in the mid 2000s. George used to be teach workshops at Cone Editions back in the early 2000s. LCD was still a bit new -etc - and we certainly did not employ the NEC and Eizos that we do now. The workshops were filled with Sony Artisan CRT calibrator reference displays.
Viewing Soft Proofs is only as good as the quality of the calibration being used. With a NEC or an Eizo reference display using their own calibration - you can reliably soft proof. Using anything else - your mileage may vary. Adding on a calibration software such as Spyder or X-Rite is not actually calibrating the display. What these do are to actually limit your computer's video output and doing so actually reduces the ability to reliably soft proof. It goes against logic but it actually is quite logical that if you reduce the fidelity of your video output in your computer - you limit its ability to display.
The Eizo CG series and the NEC Spectraview series include their own software that is used to calibrate the actual display and bypassing the computer's video board. These types of displays have on board 14 bit video engines. Your computer video output remains null. The Soft Proof is unaffected by your video output. The display because it has 14 bit output can be calibrated to your selected 8 bit target. Your computer only has 8 bits to begin with. Setting a calibration target necessarily reduces that - and sometimes severely.
Without a system like these reference displays - it is possible that checking or unchecking those settings may work "better". With the cost of refurnished NEC Spectraviews - there really is no compelling argument to use an Apple display or any other display that is not a reference calibrator type with onboard 14bit video engine. They just work so much better. They do not have the bells and whistles of Apple new sexy displays - but Apple built them for video editors not image editors. Video editing is sexy. People who print are now the exception rather than the norm! We're like curmudgeonly fur trappers in comparison to video editors who want hugely bright displays! People who edit images for print need very limited brightness displays capable of reproducing 256 gray levels each of red, green, and blue set to a very specific gamma, white point and brightness. Tack on a Soft Proof ICC and that calibration must be very accurate indeed.