First, this segment:
...has a couple sections where the gradient is 100% plus!
Second, the leaders times at about 16+ mph seem about right.
If anything, they seem a bit slow for "leaders" on the segments (fast for me, but not some I think of).
Third: we have a weekly training ride (Montrose Ride) that, if there's less than 100-riders riding it, that's a small turnout. Yet Strava only has about 20-30 people reporting having ridden it that week.
In conclusion: Strava isn't accurate nor reliable because a) it's data/interpretation is faulty, and b) not everyone reports/uses Strava, and c) those that do aren't always the fastest/strongest.
Therefore, don't draw any conclusions from Strava.