It's a strange attributional convention used in headlines and links by some publications. I've never understood why, as it reads so confusingly, snd the reverse

It's a strange attributional convention used in headlines and links by some publications. I've never understood why, as it reads so confusingly, snd the reverse usage (source: topic) seems readily and intuitively available instead. But it's still common to see (topic: source) in certain house styles.