Japanese fujos treat yaoi like most men treat lesbian porn. Something to wank to and fuck off, not something to aspire to become. Also worth noting if you're talking about jap fujos that in Japan the word doesn't have the same gooner connotation that it does in the west. Over there a fujo is just someone who likes yaoi instead of in the west where fujos are women obsessed with it.
Try to remember that it’s 2025, not 2005, so many men seem to respond to lesbian porn in the exact same way women are responding to BL - by trooning out.
As for why the Japanese Fujos don’t do this as much as western ones, I think there are a few factors
1) Japan is a shame-based society whereas most Western nations are classed as guilt-based. Meaning westerners tend to think something is inherently wrong or evil even if no one catches you OR even if the truth causes problems. Asian nations it tends to be wrong to embarrass someone in your in-group or to cause shame to your family. Both have their pros and cons (for example Japanese people don’t think it’s morally wrong to lie in and of itself which can cause some problems, all the cheating and scamming that come out of Asia)
2) This relates to yaoi in that yaoi/bl is a guilty pleasure - in Japan, it’s fine as long as you hide your collection and interest irl. No inherent guilt as long as you’re not flaunting it. Whereas in the West, female fans had more mixed feelings about it - in the past it was more, am I allowed to read this as a Christian? Now it’s, am I allowed to read this as a straight woman?
3) Japan has been officially publishing yaoi and BL since the 70s, so there has been infrastructure there to let female creators create and get paid while selling to a female audience. In America there is no infrastructure so it’s been mostly an online phenomenon - no editors, lots of self-promo.
4) Yet women were creating just fine, until the “Own Voices” movement came in along with SJWism. At that time having the right ~identity~ seemed like a good way to get instant promotion online, and straight white woman wasn’t fashionable. The Church of SJWism decided that only gay people could draw yaoi despite that never, EVER having been the case. And it also declared that being gay or trans was morally correct and fashionable (therefore very promotable). At first I personally noticed fujos all pretending to be bisexual. But that wasn’t enough, because they were women sexualizing gay men which was somehow deemed sinful in leftist circles. So at that point a lot of creators and readers were kind of guilted into becoming trans. They also thought it was a great way to promote their works.
Having been in Japan recently, the trans stuff is getting in due to internet (but there’s a language gap because they are bad at English) and social conditioning but at a slower rate, and many would-be pooners just won’t go the distance because it will bring shame to their families, plus less of a push from the schools.
I also think we here in America were lacking some distance from our arts and entertainment. It’s really pushed here that movies, tv, books etc are Important™ and we should somehow learn Big Messages from them. The best example I can think of is Star Wars, people treat that slop like it’s a religion. Maybe guilt-based societies have a harder time treating arts and entertainment as a frivolous pastime, and try to justify their enjoyment of it in moral terms.
We should treat 99.999% of entertainment the way horror fans treat their b-movies and pulp fiction. Give it no special importance, just enjoy it in the moment then move on.