female genitalia differ in elasticity, diameter and length....

just as do male genitalia  -   it is impossible to declare a "perfect size" for all women....

fortunately the female organ is widely tolerant in most cases

if you read some of the many studies of what women prefer, it's all over the place - some prefer more length but cannot tolerate diameter,  some find length wasted but crave diameter,  some like average whatever that is and some are real size queens

probably a very wide variety of male and female genitals are "a perfect fit" because of the females elasticity and tolerance

You just may see funny faces if it's too long and wide lol. But after a while, I really enjoy it.

A tighter fit is generally a better fit, IMO, though I have met ladies who were so tight that it was painful for them and the session was a flop for me. But the thing is that with ladies I have seen more than once, the fit is not consistent. Pussies seem to relax and contract at different times. Have not made a study of it, but I believe some of it is cyclical, some relates to level of stimulation (both how excited she gets, and how much one works her) and I am sure there are other things that enter into it, too.

A long time friend recently apologized, post-orgasm, about how her pussy gets bigger after she comes (yet another reason why it is in a provider's interest to fake it rather than really have an O?!). I was having fun and had not noticed until she pointed it out.

And that is the real point - yes, the physical fit, the right tightness, does enter into it, but the main thing is how well you fit together over all. How do you move together, how do you touch each other, do you find a good rhythm in one or multiple positions that feels really good for both of you. That is what matters. So the meaningful part of the quote is how they moved together, not the "fit" per se, IMHO.

As for the normal size that a lady can accommodate - for the survival of the species, I imagine that the average range of vagina sizes accommodate the average range of penis sizes. Everything I have found suggests most guys (over 90%) fall into a range of between 6" and 7" in length, and a diameter of between 1.25" and 1.75". The mean is right in the middle of both of those measurements so you are average if you are around 6.5" long when erect and 1.5" in diameter.

Helpful?

The funny thing about it is that about half of all guys think their penises are small. That could either be simple insecurity, or modesty (I favor the latter).

zig