The title for this article is misleading. It only says they've agreed to a study to investigate it. There's a world of difference between that and actually approving a 4-day week for all.
I do see your point though - it could've been a bit clearer
Council workers are a separate group of people from the councillors who made the decision.
https://news.ycombinator.com/newsguidelines.html
(Submitted title was "Glasgow City Council approves 4-day week on full pay".)