It's definitely not just a brisk walk. Walking at that speed for extended periods of time is likely going to be painful and most people probably couldn't do it.
The average speed of 6km/h is so slow I don't think most people would be capable of running like that. So a brisk walk, or running with intermediate walking is probably a more apt description.
Edit: pretty sure I read it as 1:40 hmm
10k in 1h20m is not 6km/h on average, it’s 7.5km/h
And no one has mentioned gradient
The transition from walk to run occurs at about 13 minutes per mile. A 10km run in 1:20 is about 12 minutes 52 seconds per mile, which is extremely slow. This better be a recovery run or something, it’s barely enough to lift an average person out of a Zone 1 heart rate.
It's just that I remember a nice brisk 9k walk in hills which took 90mins. In 35c heat, with malaria.
Main point here is I wouldn't describe myself as anywhere near fit. And "most people" is not a healthy benchmark, sadly.