I don't think there was so much traffic on these stairs that you ended up forced to one side the whole way. The forward distance travelled is also trivial in t

I don't think there was so much traffic on these stairs that you ended up forced to one side the whole way. The forward distance travelled is also trivial in terms of effort compared to the height displacement upward. Most people can walk for 10 minutes without breaking a sweat, but way fewer would feel fine walking up stairs for 10 minutes. Not to mention, you can simply have a convention that the downward walker on a spiral staircase favour whichever side is best.