I have noticed this as well in therapy.
On the other hand, my mum, who probably actually is a clinical narcissist has access to a therapist, and is less than truthful or honest with them, and so the therapist can only work with what they're hearing, and it just provides her with more tools for narcissism and emotional manipualtion.
There's been a lot of "my therapist has advised me to do X when you say Y to me because that is unkind and hurtful to me, and I deserve better". - simplified for the sake of mumsnet, but pretty much along these lines. Usually when calling out batshit behaviour.
I know real life is not the movies, but before I had ever experienced any sort of therapy, I thought therapy would be like, you tell a therapist your problems, you let your woes out, and they genuinely call you out on your bullshit in order to allow self reflection.
Instead, it's a lot of validating your feelings even if some feelings probably shouldn't be validated.