It's been a while since I read "The Perfect Protein" by Andy Sharpless, but IIRC their argument is that it's not just fish, but particular populations of fish. Some wild fish are fine to eat - others are either at risk or are keystone species that shouldn't be wiped out. Also the method of fishing makes a difference as well. Hence the contrasting advice.

I wonder if anchovy and mackerels are overfished. I'm not sure as we don't see them often on the table and there's few reports outside of California.

In this specific case, even if they wouldn't be the best food source in general, they would still be better than salmons (which we eat plenty of) in terms of food efficiency.

This notion of shortcuting the production cycle is really intersting to me. If for instance instead of drinking milk we'd get equivalent nutriments from straight eating grass based products, that would open a lot of ways for improvement.

They're giving advice based on that's good for the individual, which can be at odds with what's good for the collective.

Not all fish are overfished. Even salmon isn't overfished in all regions.

We can't. The fishing fleets are on a path to totally wiping out Herring in the Baltic Sea for example. So the article misses the point on that front too. The government of Sweden is doing nothing while the population collapses.