Whatever stigma exists in someone's head can easily create false reportings.
"I don't want to feel like a ________"
There are many options to fill in the blanks.
Well, that's true. I can understand how a woman might under-report. You tell your women friends virtually everything, however, more than you would tell your husband about these matters probably.
In my neighborhood when the children were little, and given that most of the husbands worked in the city and didn't get home until about 8, the moms, who either didn't work or worked better hours, would meet at one mother's home at about 5PM. The children would either be down for a late nap or rampaging around the house or with the au pair. Then the alcohol would come out. I barely drink, so it was more a case of listening. The same thing would happen summers at the pool club. Their husbands would have been appalled by some of the things which were revealed. I could barely look some of them in the face after hearing things I shouldn't have heard. I may be wrong, but I don't think men tell their friends these kinds of things even if drunk about either themselves or their wives.
Think not as rich, not quite as narcissistic, and more honest "Big, Little Lies". I swear to you, some of those characters had to be based on women I knew.
Ever since the big scandal about how the results of a large percentage of psychological papers can't be reproduced, my already low degree of faith in their reliability is even lower.
The Kinzey report I never believed. For crying out loud, most of the data came from prisoners.
As for the Masters and Johnson report, the initial participants were all prostitutes paid to perform sexual acts while hooked up to machines. Later, they were married couples. I'm sorry, but could married couples willing to do this, perhaps switching partners, as Masters and Johnson did, "for the science", be a good sample? Although, given that most of the research was into physical changes in the body perhaps it didn't matter.
I trust my informal survey more. In vino veritas.

I admit, of course, this also might not have been a representative sample.