For one, those are average figures from the data that users provided. The less users provided info on these games, the less reliable it is. Some of the games you picked only had 1-7 users provide their data; that's very low, and it's reflected in the color of the bars with the average time in it (red means less reliable).
Second, every user has its own speed and playstyle. The playstyle is reflected in the distinction between main story, main story + extras and completionist. There is no category for speedruns though, so you can't compare these averages to speedrun times. That being said, some people can take up to 3 times as long as the average player in every category, not necessarily because that's required, but because they just like to take their time.
Generally, this site is not about how much time is
required for
you to finish a game but about how much time other players spent with the game. You'll have to draw your own conclusions from that. If you notice that it always seems to take the average player twice as much time as you would need for your playthrough, you could adjust your expectations accordingly and half the time. It's not an accurate tool, just a point of reference.