RV-12s with the Rotax ULS do not have over-voltage protection. Luckily it seems that the Ducati Regulator fails with low voltage, not high, at least so far.
Over-voltage protection is mandatory for aircraft with the EarthX battery. Both EarthX and modern avionics have built-in over-voltage protection. But they have their limits. A runaway alternator can exceed those limits.
If your plane does not have over-voltage protection and an over-voltage condition does occur, would you rather have a switch to immediately disconnect the charging system, or would you be content locating and pulling the alternator fuse? I ask because the latter method has been proposed. or so I have been told.