NO, no , no .

THe factory regulator does not reduce 12v to 5v . It just switches the 12v supply on & off regularly, like a turn signal unit, so that over a period of time, the gauges will 'see' an average of around 5v . If you put a meter on the line you should see a sequence of 12v , 0v , 12v , 0v etc etc .

An electronic replacement regulator WILL put out a constant 5v , but this is absolutely not what the factory item does.

The gauges will function roughly the same with either method, as they use hot wires and react slowly to any voltage change.