A refreshed New Tab layout is being rolled out to users in the US and Canada, featuring a repositioned logo and weather widget to prioritize Web Search, Shortcuts, and Recommended Stories at the top. The update includes changes to the card UI for recommended stories and allows users with larger screens to see up to four columns, making better use of space.
Well, they call it "progressive role out" , this is what they say
Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.