OK, but that's a huge caveat that is never stated when we have this discussion, isn't it? "Don't talk to the cops when they're investigating you" is massively different from "don't talk to cops, ever".
And yeah, I know, it may not always be obvious whether they are investigating you, especially if they are willing to lie or be deceptive. (If they're really investigating you, you may not even realize that you're talking to cops.) On the other hand, it might be clear enough sometimes that they are not for me to be willing to talk to them.