I’ve read that too. I do like the concept of “effective reps” for this reason - there’s several ways to skin the cat. At some point, you have to do some threshold of hard reps. Get there with fewer, harder sets or more, lighter sets… but you’ve got to get there.
These concepts seem easier with running (I assume; I’ve at least seen what running looks like). We understand if you’re going to go full bore on a 400m, you’re not doing a ton of repeats. If you go 65%, you’re probably trying to accumulate a little more mileage that day.