They show parts of the ride with the highest average speed. For some people these can be useful stats i.e. if they're riding in the flats. I agree there should be an option to drill down to that exact section.

Thanks for the feedback; so it's only applicable to that activity? If so it seems weird that it'll break up distances as "best efforts" if you'll only have one effort of each distance or measure per activity 🤔 🤔🤔 🤔

Yes, it's only for that activity. The best efforts that considers all activities seems to be a work in progress, Strava had that online for a short time some days ago but now it's gone.

These are showing best efforts so there can only be one for each distance/power/uninterrupted elevation.