I'd love to hear more about this also---particularly because what I've seen in classes is that it makes things worse.
Maybe I'm thinking about a different grip.
There are some people out there with weak grips that simply won't ever practice much, so teaching them technique that will result in optimal performance given sufficient practice is not nearly as important as teaching them a technique that'll be decent enough for them to get shots on target while being safe when they don't practice much. So---if the crossed thumbs grip can help those folks, I'd like to hear more!
Like I said, though, particularly with smaller pistols (9mm in a subcompact size, as an example), that's not what I've seen---or when you say "pocket pistols" are you meaning tiny .32s and .22s? Either way, I'd like to hear more if you've got the information to share.