If you have an unplayable extra ball on Metallica, then you are already not playing by the full IFPAPA rules (which is ok, except under certain very specific circumstances). Which means a TD could potentially apply a ‘house rule’ here to let everyone do whatever the TD desires.
The IFPAPA rule set is designed to provide a standard set of rules that a majority of pinball tournaments can follow. It is set up so that players know what to expect when they show up at any tournament, to try and standardise the experience. IMO, if a rule doesn’t fit your event, house rules can take precedence as long as all players are aware of the exceptions.