I haven't seen many if anyone say that, more like "if you were sexual or orgasmic pre-op then you will likely also be after". I've also seen a lot of women who need to adjust their hormones to have enough libido to feel sexual arousal.
For my part I very much wanted to be sexual after however I also decided that I would be happier with my brain fixed (HRT) even if my libido was impacted -- and for the first several months of HRT I had very little sexual desire so I felt I had an idea of the possible downside.
Post-op I'm even happier, I clearly had effectively suppressed genital dysphoria far more effectively that I'd realized. At 6 months post-op now that the pain is reduced (not gone yet, my left labia are a bit sensitive). I first started really enjoying sex at around the 4 month point and while I still haven't gotten to orgasm, the pleasure I do get from sex play is excellent and so for now I'd compare myself to an anorgasmic cis female. How I respond now is so much like women I've been with in the past it's kinda scary.
I hope you find what you are looking for, i forget the numbers I've seen but certainly not all women experience sexual satisfaction post op. I feel my surgical result was on the above average side (my electrologist who's probably seen more both cis and post op vagina's than many surgeons said my results are a lot better than most she's seen)
OP, I've had some more time to think on this. On HRT my libido was initially killed nearly dead and came back only when I started on progesterone -- caveat lector, medical studies say this isn't true across the board. I've also found that if I cycle P I lose libido whenever I'm off of it. One day I will make some placebo tablets and do a double blind test on myself but I'm in no rush, ymmv IAC.
If I'm not feeling sexual, I can't will myself to enjoy stimulation and that has been true ever since I started HRT. It's so different from what it was like when I had testosterone in my body when almost no matter what my mood, if I chose to stimulate myself, I could become fully aroused.
I don't plan on testing this, however if I were to knock off E tomorrow and start injecting T, my sexuality would shift to the same way it ran for the 40+ years before I decided to medically transition. I believe this mostly because I've known a few ftm trans men all of whose sexuality was changed to typically masculine when they took T.
Lastly, if your clitoris is actually numb -- as in no feeling then yes that can be laid on your surgeon, however I know for a fact that humans can learn to orgasm without touch, sensation etc. So if you're approaching clit, vulva without first having a spark of interest that alone could explain lack of response -- and on the other hand, once I'm aroused, even the back of my hand becomes an erogenous zone.