The whole point is that allowing variables makes it fun, and allows people to use what they know best.

Another major issue (imo) is that the judges can only judge the edge and not the technique used.
The judges don't care if you can only hone 1 razor per month under a full moon after a week of fasting and meditation, using only a concrete brick. If that razor would have the best edge, you'd win.

The more someone tries to make it 'fair', the less fun it would be imo.