Ok, that was the rational bit.
FWIW - as pure anecdote, my ex-DH was subjected to 'cry it out' and a strict feeding and sleep regime back in the 70s. On the surface, he is a likeable, well-balanced, happy man. But, underneath, he has difficulties with depression and insecurity and suffers from an inability to express his emotions by, eg crying. To make it worse, although he cannot express his feelings well, he craves physical attachment such as hugs and cuddles.
I have not one shred of evidence but it would not surprise me one bit if the regime that 'taught him' to sleep through the night also 'taught' him that there was no point expressing how he feels because no one is going to respond anyway. After all, his mother didn't pick him up when he cried as a baby, so that's what as become the norm to him. I suspect that they only way to unpick that is via expensive therapy.
So, personally, I could not subject my DS to any form of sleep training. Purely on a precautionary basis.
I completely accept that this is a totally anecdotal post - but then there are lots of anecdotal 'CC worked for my DC' posts here too.