Indexing is something one can check with the right tool, yet fixing an out-of-index crank as mentioned isn't for the average builder. Very important to check btw on a top runner. Often, cheapo reground cranks suffer from inaccurate machining yet for a grocery getter, it makes little difference.
Having crewed on a supercharged alky dragster and then a supercharged nitro dragster long ago, I found that even big-bucks forged LA Billet, Keith Black and HTC cranks will bends the throws a few degrees, especially when a exhaust rocker breaks and forces a huge spike in pressure in the dropped cylinder. Sad that a pricey $2,000+ crank can be tossed after only a few runs with a bad tuneup!