I can't tell if this is a joking or serious answer. But either way, OP, I actually agree with roughly 6 being the common upper limit in contemporary romance from my reading habits. This sub tends to draw a distinction between romance, erotic romance, and erotica, that I don't think is necessarily shared by readers/consumers. And readers don't all think alike anyway. For example, as mentioned elsewhere in this thread, some people view FSOG as romance and some view it as erotica. Most people I know would view anything "kinky" (which is different for everyone!) as erotica, and would also think a book with 6+ sex scenes in it as being erotica too, just because of sheer number, even if it's quite vanilla sex.
Even if you could somehow get consensus from readers on whether something is erotica or romance or erotic romance, it really doesn't matter anyway because many consumers aren't using Amazon's categories to find purchases and Amazon's categories aren't strictly adhered to anyway. For example, I was looking at top 100 erotica the other day and Susan Elizabeth Phillip's "Nobody's Baby But Mine" was in there. She writes relatively clean romance! I don't know anyone who'd think that book is erotica. Or whilst researching historical BDSM erotic short stories the other day, I found several governess BDSM porn stories in British Classics!!!!! Made me laugh!
I have read one to two contemporary romance novels (occasionally paranormal romance) per week for the last 20+ years. Everyone's preferences are different. Personally, I like books that have 3 to 6 sex scenes in 50-80k words. 2 or less sex scenes and I tend to feel cheated! I can usually tell what I'm going to get from the book's blurb, prior experience with the author, reader reviews, the book preview/look inside, and the number of pages. Occasionally this doesn't work. For example, a recent purchase by an erotic author had NO sex in it which was totally unexpected! And another author who normally writes quite steamily chose to build the sexual tension and not have the first sex scene til three quarters through. I was antsy as hell by the time it arrived!! And it was a huge let down when there was something in that sex scene that was a turn off for me.
I can't really offer advice as a writer since I'm a noob, but as a reader, I'd just recommend giving hints to your reader about what they can expect (eg. a ripped man chest on the front cover suggests steamy to me, so I'd be annoyed if the sex scenes are all fade outs) and either keeping it consistent with the genre in which you write or indicating to readers that it's not, so that they're forewarned.
HTH