No real way of knowing without testing all shafts, all flexes, in multiple lots. We have a lot of data on a lot of shafts, but not all of them. Also understand, that butt frequency is not always going to match what the flex designation is. This is because the flex distribution from the butt to the tip can be different. For example, you could have two shafts that have a butt frequency of 250 and one be designated an R flex and one an S flex. The R could be more flexible as yo move down the shaft, even though the butt frequency is the same as the S. That is why we like to do the zone testing to get basically a poor mans EI curve. the zone testing is a quick way to see the flex distribution at different points on the shaft.
All that being said, I do not think you will see very many shafts, same model and flex, vary by more than 5 cpm’s in butt frequency from shaft to shaft. Some will, but not many. Different models in the same brand, you might.
Here is the link to the flex range charts Jim and I put together a few years ago.