Beyond this sentiment just being obnoxiously repetitive in these comments, it's also plain as day to see why this might be different. The projects in that link don't have a fixed, set date that support will be extended to from the get-go as a selling point. This phone does.
I wouldn't expect a Google messaging app to be around 8 years from now, but they've been selling Pixels for 8 years and have always delivered the promised updates.