And coincidentally, all of the other girls who marked down high scores on his romantic-interestingness scale, plus one who hid herself and is the traitor, will all have equally impossible and un-realistically-evolvable sexualities configured around the exact details of his unreasonable preferences.
Keltham doesn't say anything about 'how convenient', because this is not, on that hypothesis, Carissa's own fault in any way, nor would she have the ability to explain it. Unless it's the other path to the same end, Chelish Governance faking an elaborate ero-LARP around him.
Or on the less literary hypotheses of reality - maybe dath ilan has no masochists because nobody ever tried following up severe nonsimulated violence with sex? He wants to think it can't be that simple because somebody in Civilization really would have figured it out and then figured out a less costly way to get the same result. But if it's some weird brain thing you can't guess from parts of the model pinned down by other observations, maybe they really wouldn't have figured it out.
"Aw crap," Keltham says. "That reminds me. I wrote down a list of my pending questions that I managed not to ask you during sex. It was in my bedroom. I wonder if it survived the invasion. Or I wonder if Security picked it up. I used a second-layer-of-naughtiness infohazard cipher to write it, which is the highest level of cipher I can read reflexively. Is Comprehend Languages going to go right through that? It's legit kind of personal."