It seems to be an American thing. The British/Australian/New Zealand SAS guys have been doing all sorts of crazy stuff since 9/11 and you rarely hear a peep.
I know of Aussie SAS guys from the Vietnam War who still won’t talk about what they did because to them keeping secrets means, unless ordered otherwise, you take them to your grave.
Mind you, not all American SF are big talkers after the shooting stops. It’s just that the ones who do talk, talk a lot and loudly.
A good many of them were Warrant Officers when I knew them. Damn fine bunch of fellas.