There's a mixture of both. Purists seem to be a bit of a minority at this point, but we DO exist
That being said, the majority of restoration threads don't really center around what a restoration truly is.
If you look up restore or restoration in a dictionary, it's clear that you're returning something to original condition.
You're not changing it. You're not 'improving' it. You're making it like it was originally made by the manufacturer. It's not perfect It's not 'better than new'. It's not new playfield, cabinet, plastics, ramps, everything but the wiring harness etc - it's fixing the original parts so they are like they originally were.
I'm not saying that's right or that's wrong. That's completely in the eye of the beholder.
Coin Op games were meant to make money and be enjoyed. My theory is, let people do whatever they want to with their own games, so they can enjoy them more.