If by cancelled you mean "ended", then it was cancelled. But the reporting at the time by the network and the creatives was that they decided in advance of writ

If by cancelled you mean "ended", then it was cancelled. But the reporting at the time by the network and the creatives was that they decided in advance of writing and filming the fourth season that it would be the final season (and that the approximate length and arc of the entire show was worked out years prior to be around 50 episodes), and so the ending was written deliberately as a series finale, thus making it not an example of what the upthread people are talking about.