Strava

But you said:

His/my point is surely that it's not all really effort? It's just easy to think of it as such.

Anyway, you're right, it has nothing to do with Strava :)

Did you read the article? His point is that if you want to increase your fitness the key is not to add in loads of middling intensity work but to add in focussed high intensity stuff.

The reason being that junk miles are effort- just the wrong sort of effort.