Honestly I think many people without mental illness have thoughts doubting their relationships with and feelings towards loved ones, even their children, at times, or their roles in parenthood, and I think violent thoughts when angry are also pretty common.

I just think that people with mental illness who are undergoing treatment are way more likely to do a lot of introspection and be very vigilant about their thoughts, as well as to share those thoughts with professionals. If anything I think often the mentally ill have a much more grounded and honest representation of themselves as humans than the average neuro-typical, since we go through so much exposure and vulnerability by default.

Any psych professional worth their salt should understand this, and know that it's only red flag time when there are plans and intentions.