Unfortunately I had never had sex with Japanese women, not even prostitutes, so I'm not speaking from experience. Perhaps there's some serious study out there, social science, gender study sex study or something. Comparing the amount of verbal (words) and non-verbal noise made by man or woman comparing different countries and cultures.
But consider this, from foreigners learning the Japanese languages and ways. In some context Japanese put huge values in silence, an extreme example, when one commits suicide by slicing open his own belly, he should be silent. In other context, it is impolite to be quiet.
In friendly conversation (i.e. non-formal occasion) if A is talking and B is listening, B should not be silent, s/he must continuously make noises and words appropriate to whatever A is saying, to express that s/he is paying attention and engaging. When eating, especially if the person cooking or hosting is present, s/he must making eating slurping and swallowing noises, and the louder and ruder it is, is expressing s/he is enjoying and appreciating the food and hospitality.
By extension, I'm guessing Japanese (both men and women) are deliberately making a lot of noise because it is polite to express appreciation and prowess of the intercourse partner. Especially the woman should be noisy to make the man feel good about himself.
If you compare today's JAV to more than, say, 8 years ago, I think it used to be even more exaggerated. Now there's a slow trend to have women more to be herself and less performative during sex.
