When it's only negative distortions they are against and often even just negative thinking in general even if it's realistic.
Not every negative thought or idea is a distortion, especially if you grow up abused, then that negativity just is your life.
And research shows that "mentally healthy" people have plenty of positive distortions. They overestimate the likelihood of positive things happening (optimism bias), they overestimate their control over their life (illusion of control) and they overestimate their own abilities (illusionary superiority). But you never hear therapists discourage those distortions, they might even encourage them. Showing that they aren't actually against distorted thinking.
I hate this toxic positivy that therapy promotes.