I have a 4-inch penis. I don't ever remember any woman saying she came because of the motion -- or that she "didn't cum because of the motion" -- but many have have said because I'm "an attentive, caring, and skilled lover", or words to that effect; some have thrown in "creative" and "fun"; some just because they think I'm "a hunk"; and many more because I have a fantastic tongue.
I totally agree with
@Pficcie255:
I particularly go along with "There is no universal way to make a woman cum every time." That's what I meant by creative. I've heard guys reel off how their secret formula in screwing a girl, like the steps in assembling a piece of furniture; I find "listening" to what a woman's body is telling you is the secret of success when it comes to sex.
Yes, it's true "some like to dom and humiliate to get turned on and so prefer small cocks", and that can be really hot, but I've found many just like small cocks.