The 200 gram weight we use is what we started with years ago when collecting data for our data base, so we have continued with it. It doesn’t matter as long as you compare shafts using the same weight, whatever it is. If you want to compare numbers using a 200 gram weight vs a 205 gram weight, the difference in the number would be about 2 cycles (248 vs 246 for example).
The chart was originally done based on clubs with grips installed and it was created based on the averages of hundreds, if not thousands, of assembled clubs that were tested. FM Precision, the original company that came out with Frequency Matching (invented by Dr. Joe Braly for FM Precision), stated that there are 10 cycles between flexes. This was true for their shafts and presumed to be true for all other brands of shafts. There were not a lot of different brands back then. Fast forward and consider True Temper shafts. Some of the TT models have 12-15 cycles and we have seen other models even more. Some even less. That being said, 10 frequency cycles when measuring the butt frequency of a shaft is what I personally identify as a full flex.
With regards to the chart, we generally advise to use it as a flex reference (when comparing the frequency to the letter flex designation) for gripped, assembled clubs only. The chart also allows you to see the progression form club to club in a set as the lengths change and also gives you a visual reference when comparing clubs. So, where the letter flex designation is located on the chart is not the exact point of flex change. That can and does vary from manufacturer to manufacturer and sometimes from model to model. We have the wood and iron charts with color codes that show the range you can get in frequency for each letter flex designation based on all the shafts we have measured in our shaft database. I will get that put on our website in the next week or so. I think it will be helpful.