The Bug.
Dying through being harmed using a potion while getting killed by a mob for ex (Husk) will preview death msg : "Death.Attack.Magic.Player".
Linked issues
Comments

Are you sure this affects 1.16? According to MC-133088, it was fixed in 20w07a
Oh, very sorry. Though i captured this many days ago as i forgot what version i was in i must have misunderstood. very sorry.
Cannot reproduce.