No, unfortunately the Watcher documentation for monitoring Marvel indices are out of date. Those examples were all written for a Marvel 1.x index, but you are presumably using Marvel 2.x.
We're in the process of fixing a large amount of the docs, as well as automating the testing of our scripts in the docs, but it will take time unfortunately.
In the case of that specific watch, it's not going to be possible as it's written because we do not track cluster events like that in Marvel 2.x/5.x. What you could do is to monitor the
.marvel-es-1-* (2.3.x) index and
cluster_stats type for its
You can choose to get fancy with it or keep it simple to just detect losing nodes (if that value is lower than you expect, then follow the rest of the path).
Long term, I suspect events will make a comeback, but doing something "simpler" is likely the best approach for now.