It’s not about distance, it’s about movement repetitions. Imagine having such strong opinions on matters outside of your expertise.
Steps seems like a reasonable measure though? It seems reasonable that each step results in similar exertion for any person. Distance, OTOH, would be affected by the length of your stride (-> your height), so it might be a worse measure.
Well, every person with a cell phone can open it right now during the article and see how many steps they've taken on average in the last week, month, etc.