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Thing is it's hard to get used to RGB numbers especially with a decimal point compared to reliable CMYK numbers. It is not about a calibrated monitor as that is a requirement. I haven't seen any monitor that doesn't drift, nor with fatigue that you can reliably say what the safe values would be visually. Of course if you can get used to rgb numbers so much the better. Yet I can't , having done too many years of press pages. Don't get me wrong, I was the one who wanted all the digital stuff workflow etc. I worked with many companies on making calibration and profiles easier to use. I fought and lost many a battle with prepress over acceptance of rgb files. Yet one thing that is all telling in skin tone is how much saturation you have by simply watching the Cyan values.
While here I have to say that white balance or preferably gray balance is helpful in variable light but with reliable flash in studio not really necessary. Variance in light, light incident angle, etc make it trickier than using a preset ( only if you have stable flash like Broncolor or ProPhoto.)