This is currently working as intended. Hopelessly damaged ships like the one in the savegame are auto-self-destructed (auto-controlled, damaged, no hyperdrive, no other movement, etc).
However I think that this feature is too confusing, so will disable this for player ships in the next update.
If it's working as intended for a reason, then I don't see any reason to change it. All that's necessary is that a message be logged for the player - "Ship X was hopelessly damaged and has been scuttled by the crew.".
“That which can be asserted without evidence, can be dismissed without evidence.” ― Christopher Hitchens