An important concept , and one that also has implications for mental health treatment. Eg, many talk therapies operate under the assumption that 'saying the wrong words in your head' is a factor maintaining the problem, and replacing these with better ones will result in improvement.

But since words are not thoughts, and further they are not mental actions (such as relaxing), saying different words in your head is only useful if they help put you in a frame of mind where you can access, or discover, the right thoughts or 'mental actions'.

I conjecture that within the diversity of human minds, there are some for whom language closely bound to thoughts and mental actions, and others less so, and that talk therapy is more useful for the former than the latter. If this is true, then it is also likely to be the case that most talk therapists are of the former persuasion, since they are not likely to espouse a practice which has no effect on themselves.