Why woudln't it be? PPF is simply a measure of the amount of photons going in. It's like filling a bucket with water. 10 liters is 10 liters.
Of course some lights will be closer to the wall and have more wall losses than others, but of course you can adjust for that as well. A bigger room will have less wall losses than a smaller one.
Professional grow rooms are designed with software that predicts PPFD based on the lights used and distribution of those lights..
Incorrect. PPF would be photons emitted at source, so going out. In order to fill that 10 liter bucket, it would have to catch all of the light. If the bucket had a small radius (think a tube) you will have to have a much higher PPF to fill it since on part of the light source is going into the bucket. You are even wrong about wall losses - with the same light source and all other things being equal, a larger room will have more total wall loss than a small one. That is just simple math.
I actually know what you are referring to about reflectivity - yes it does have a significant influence (you can 'redistribute' stray photons recovering up to 80%) on overall PPFD, however you should understand the basics first. PPF is for light source (great for vendors) and PPFD is for gardeners, more importantly, plants. Once you get those settled, we can work on reflectivity ok? I have some interesting numbers on various materials and paint colors.
You are correct that there is software out there to help predict PPFD; it is used for planning. In fact it can be, and often is, accomplished the same using excel. People are already starting to do that on these forums. One member has even gone so far as to visualize the overlap.
As to your comments regarding the text published by Cambridge University Press, its speaks volumes about your character and ignorance. Cambridge is the world's second oldest english language university and a world leader in plant research. Stephen Hawking is a professor there. Any normal person would consider it to be an expert source for factual information.
Anyhow, this isn't about who is right and/or wrong but about the sharing of ideas, concepts, theories and other information for discussion. Personally, I am fine with the rude comments so long as there is benefit to the discussion. It is fairly easy to identify and ignore the ignorant but you still want to see them learn.
Back on topic:
Does anyone have, or could take, measurements for individual light sources of the following:
Vero 18, 29 in 2700k-6500k
CXA,B 3070, 3590, 2700k-6500k
Citi 1212s, 1818s, 1825s, 2700k-6500k
It would be good to collect all this information to get a better understanding of what each light can contribute at what height covering how much area. It will be a lot of info considering all of the different variables but it will be a very good tool for the DIY community. Cobkits has already provided a lot of data but much more is needed. Keeping it all out in the public allows anyone verify and use that data.
Why? It is a bit of a silly question, but it warrants clarity. The answer is to be able to provide the best community vetted guidance on how to build a light source for your environment. It's accuracy will be dependent upon the community providing real world results for commonly used components.
How? Post your results. Measurements come with information about the measure, height, coverage, reflectivity with temperature and other variables as secondary data measures. As more results are posted, the community will standardize on how best to measure going forward.