I have to wonder whether children like my own (I won't say "ours", not knowing every else's kids personally, but that was how the sentence started) are on average less likely to be ST-able and more likely to be traumatised by it?
We have also taken the NCSS (or similar) path with all three kids. My second child was my easiest, but as I have said in a previous discussion, the one time I decided that she was not getting out of her cot until nap time was over was an unmitigated disaster. I sat with her while she screamed for 2hrs, she did not let up the whole time, she then did not nap again for over 2 weeks, even without the battle. She was very distant from me for some time afterwards as well, her trust was appreciably damaged. Conversely If we came at her gently and side on we could usually change her sleep habits in 3-7 days.
Sample size of 1, but my first and last child there would be even less chance of it working. And I am sleep deprived and it does cause problems, but less problems than is involved with listening to them scream or being rejected by my child because they feel I have rejected them...
But I suspect that many kids don't react like that and that STing might in fact work fairly well for them. I also suspect it helps not to have sensory issues or any other issue that makes sleep harder than average, as compared to simply having gotten into habits that need to be addressed.