I am an NCCA member and IICRC trained along with having done around 20 other traing courses during my 30 years as a CC. I know what the schools teach as per the book. That is how they have to teach. It is like anything else, you get the training and education, then over a period of time, you learn by practice, how best to do it, to achieve the required result.
This may well not be, absolutely, the way one was taught, but it is the way to get the job done and with the right education it is possible to try things out without risking disaster.
If the item is a real minger, why go round the houses attempting to clean the thing as safe as possible, when all they want, is it, clean. Having said that, if the item was only slightly soiled then a water only rinse may do.
I have only ever had a problem with 2 suites, and they were both Ph sensitive fabrics. They were both of a green coloured fabric, and acid turned them pink/red in places. Imagine what an acidic rinse would have done!
This was a new phenomenon in the trade when it happened the first time, and ended up an insurance claim, as no one knew what had happened. A few years later it was known about and the second suite was easily put right with a spray application of Sodium Bicarbonate.
Dave.