The problem with trying to come up with a way to say "this book has sex in" is that there's loads of options which all mean different things and none are perfect. Like...
clean/wholesome vs dirty - obviously this one is bullshit, we don't need to talk about why
smut/smutty - a classique. Pretty good, but feels like its falling out of favour.
steamy - as above, really. feels slightly more vague, makes me assume it's sexy but not explicit. More dated - been replaced by spicy.
erotic - erotica is a whole genre to itself, with different parameters to romance. Conflating the two weakens genre defninitions for both.
explicit - does what it says on the tin, but risks sounding a bit clinical. If steamy is make outs and fondling, explicit is genitals getting described up-close.
spicy - gets a lot of complaints, but lends itself well to a rating scale and is very popular
open/closed door - this is a good shorthand, but not very familiar to people who aren't reading romance. Again, doesn't rate very easily - a closed door is a closed door, but the open door could lead to either slow vanilla missionary or a full-on BDSM scene.
porn/pornography - comes with a lot of assumptions which makes it harder to use in certain spaces. Sits at the 5/5 end of the scale in my head. Similar to erotica in that its a distinct genre.
saucy - this is just a Carry On film. no one is aroused.
sexy - too vague. colin firth fully clothed in a pond is sexy. gwendoline christie in plate armour is sexy. that one fish from finding nemo is sexy. brushing hands described in the right way is sexy. could mean anything.
this book has sex in it - literally no
Then you've got the problem that websites like tiktok and instagram, which is where most marketing happens, can surpress content that's too sexy, especially if its queer, and authors are being forced to be over-cautious with the words they use.
And we also can't forget too that on these platforms you have to catch people's interest really quickly, and often they might not read the description. So you have to catch people as quickly as possible, using as few words as possible.
