A more accurate statistic would be:
"Only 30% of women can orgasm through intercourse. The other 30% haven't had sex with me."
But seriously from my personal experience its much higher. About 80-90% of partners have orgasmed through intercourse and the majority of them came within the first five or ten minutes.
I even had one girl apologise for cumming so quickly. I thought we agreed that this was a statistic made to make other men feel better about themselves? Like "size doesn't matter."
Size doesn't matter is an opinion, and even if psychologists ask the question, they are getting an opinion as an answer. Going beyond this opinion, some controlled studies have been done with different sized dildos shaped like penises, measuring vaginal wetness, pupil dilation blood pressue and heart rate as signs of arousal. The result was that about 7" long and about 6" girth DOES matter, up until about 8" long and about 6.5" girth, where arousal declines.
However, asking a group of women if they have orgasmed during intercourse or not isn't subjective, it's a straight yes or no. Many studies have been done, and the statistics are fairly consistent. Many women have been asked, and the majority have either never or rarely orgasmed during intercourse. And beyond a position that may stimulate the g-spot, or beyond a position which allows for intercourse and manual stimulation of her clitoris, there isn't much there that will arouse women to orgasm. Men with lots of girth can sometimes pull on on a woman's inner labia to the point where it can rub her clitoris with just thrusting and that may do it, but it is still clitoral stimulation which is getting her there.
When my wife has come during intercourse, it's been her on top and it's happened within about five minutes or so. But most times we could put her on top and do the same thing for 20 minutes for no result. It's really variable, which is why I go down on her before intercourse, and if a second orgasm from intercouse happens, then it happens. And from what I see and hear, when an orgasm happens from intercourse alone, it is more intense and more powerful for her.