It's a terminology thing. By "function", the voltage stabilizer is a voltage regulator of sorts. I suspect to avoid confusion Lucas started calling it a voltage stabilizer to distinguish it from the part of the charging system that is typically referred to as a voltage regulator.
It's the charging system regulator that may be causing your lights to flicker and that is the item which is part of the alternator.
I am surprised this is a area that would cause the inspector to fail your car. I have a similar issue on my daily driver Civic. With an older Civic light flickering is a fairly common occurrence (at least according to the message boards) yet I have not heard of anyone failing inspection for it. Perhaps it is more noticeable with the incandescent headlamps used on older cars like the Spitfire and GT6.
: I had no idea the
: voltage stabilizer was only for the
: instrument panel.