Oh, no offense taken. You're cool.
It's not about 'being quick on your feet', Glen, It's about doing instictively what you would do. Grab the rope.
If you put a biner through the top of the ascenders, it becomes essentially impossible for the rope to exit the cam shell, even in the event that a cam both opened and jumped into the un-locked (open) position so that the spring doesn't return the cam face to the rope.
With the biner in there, that, to me is a backup in and of itself. The friction hitch abve is redundant, though necessary as an additional backup.
You see, a lot would have to go wrong, a simultaneous, multi-system malfunction during a grand mal seizure, for potential injury to ensue. Even hanging, unconscious with one side of the ascender malfunctioned, I think it would not drop you.
We must assume well-maintained gear, in good working order. Does not matter if the rope is wet or dry, though.