You're right in your comments.

I was a reviewer on that paper. It is encouraging that this particular earthquake appeared to start with a fairly long interval of foreshocks with many characteristics of a slow slip episode. Left undetermined is how often such slip episodes happen, which would help assess whether spotting them is of much use in anticipating big earthquakes.

As you imply, this work is completely open - authors are identified, data is available to anyone who requests it, they had to hone their claims and conclusions in the face of feedback from other knowledgeable people, and their methods are reproducible and straightforward and make physical sense. No comparison with some of the predictions posted here.