The key has to fit the lock.
If a woman has a big pussy, she's not going to get the stimulation she needs from a pencil dick. If she has a very small pussy, a big dick will make her uncomfortable.
I personally know of a case we investigated where the lover was initially believed to have murdered the woman. Blood everywhere and he was acting and feeling guilty. Autopsy showed that she was abnormally small down there and it being the first time for both of them, they didn't realize what was happening and she literally ...... out. I also personally encountered a woman who was so small I could not get it into her at all. (6.5" and about like a 50 cent piece when erect, so not small, but certainly no long-dong Coke can either).
It's definitely not a one size fits all situation. They can stretch of course, and depending on the degree of stretch and what the woman likes, that will be a good thing. Some women like to be fisted, for example, but not all. OTOH, they're not going to shrink to fit.
If it feels good for both, that's what matters in the end. My first wife had a huge vagina, and we had great sex because we connected. But I know she would have liked to have had a bigger dick in her, and I wouldn't have minded if she was more snug.