I've always wondered about this chart. Doesn't the chart assume every woman and every vagina is exactly the same? Kind of dumb in my opinion.
No the chart does not do that.
Not a statistician but it purports to provide ranges based on the response of many women.
Kind of like a lot of things - individual results will vary.
For some women - 5 inches by 4 & 1/2 might be their ideal
Other women 10 inches by 7 & 1/2
There are a few charts that are similar but this is the one that is more prevalent on the internet.
A good starting point for the attempt to try to answer the OP's topic question and to try to answer this question
Is there an upper limit? On when bigger girth stops being better?
Yes there is such a thing as too big.
Too long
Too thick
Too much of both
Just as there is a thing as too small.
The chart may have flaws it may even be incorrect.
But I think it to be a reasonable starting point for the debate on the topic.
Never ending debate because it will never be answered to the satisfaction of some.