Many of the formulas in the edited "School of Natural Healing" are the same (in fact, they might all be - I've never compared each of them 'ingredient for ingredient'). I've only compared those I've created (and am going to create). BUT if you look at the label of the children's current products for sale, you'll find the ingredients do NOT match the ingredients listed in SNH.
I would like to add to what 'Wings said - Yes, Dr. Christopher did 'throw together formulas' "on the fly", but the way he did that was not randomly, nor was it any type of guesswork for him.
For example, I've been baking bread from scratch for over 30 years, and I rarely follow any recipe 'strictly'...that's because on any given day, the barometric pressure, temperature and humidity levels are all different...as is the freshness of the yeast, temperature of the flour/water/eggs/oil. The variables are endless. I've learned to "feel" them. I haven't had 'bread failure' for years...but if I followed a recipe strictly, I would have many failures.
Dr. Christopher understood completely what 'Wings mentioned. A pound of peppermint leaf looks like a baby's pillow in size; a pound of comfrey root looks morelike a pound of butter....and those weights will also change (sometimes quite dramatically) based on how they were dried and how dry/moist they are on any given day. He took this all into account with every formula he created.
As 'Wings said "one part" can be one teaspoon or one cup, and that creates a consistency that "weight" cannot accomplish (on a humid day "1 oz of herbs" is less volume than on an extremely dry day). So by giving us "parts" we always have the correct ratio.
Also note, throughout the SNH, you will find exact measurement and specific weights for various formula. More times than not, you will find in these cases we're dealing with a VERY specific amount of fluid of some type to be mixed with the herbs, or the herb type (fresh, chopped, dried, powdered) is specified. Many MANY times these more 'random formulas' found throughout the book, were not "specific" to Dr. Christopher, but rather, other formulas that he had used from different herbalists throughout the years of his practice.