"accident" doesn't tell you anything about what caused their death. They could have been hit by a car, stepped on by an elephant, electrocuted in the bathtub etc. They'd be better off ignoring if it were intentional or accidental and just listing what killed them like asphyxiation, heart failure, etc although that can have problems too since life insurance may or may not pay out without knowing if it was suicide

Misadventure is my favorite euphemism.

Depending where you are, misadventure isn't really a euphemism. In England:

Suicide means the deceased did something to end their life, and had the intention of ending their life when they did it.

Misadventure means the deceased did a risky thing and died, but did not have the intention of dying when they did it.

Accident means the deceased was doing a normal activity and died.

Definitions of the manner of death can be nice and clear on paper, but are much harder to apply to the situations of a person's death, so there's lots of overlap between suicide and misadventure. It's often difficult to show intent, and so those deaths sometimes get called misadventure, or they have a narrative conclusion.

I would just assume it was a euphemism for suicide