This is the scientific study that the article references.

The study took 84 housekeepers at hotels and asked them how much they exercised and how fit they thought they were. Then they tracked steps and activity for a while. Then the researchers told about half of the housekeepers that their daily work is more exercise than most Americans get. The steps and activity level didn’t change after telling them, but the ones they told got noticeably fitter and healthier!!! TLDR: Fitness level seems to be affected less by activity and more by whether or not you consider that activity exercise.