I've listened to many comments here on some of these, saying it must be assassination "because the person insisted, "If I'm ever found dead, it's not suicide!"." This is sometimes despite extensive mental health history.

Entirely possible.

But in my career as a paramedic, I've (sadly) lost count of the number of mental health patients who have said, "Yeah, that was just a glitch, I'm not suicidal, not now/nor then." ... and gone on to commit or attempt suicide in extremely short order.