With the new changes added in https://gerrit-review.googlesource.com/#/c/71051 a couple of patches were put through to update this functionality.

https://github.com/jenkinsci/gerrit-trigger-plugin/commit/5d531e6631fad490dd577fd083ba442ff23a0d95

This logic appears to be incorrect as the initial patch/functionality that there would always be a present boolean json param of 'updated' which was always present that would track the state change.
In a subsequent patch they put in optionally when the value had changed "oldValue", whilst the committer kept the same logic for this, but as the oldValue on new versions of gerrit 2.13 and later, this doesn't work as it will still fall back to the old method of checking whether to run a job on commentAdded.

Some sort of version checking appears to be the option if backwards compatibility is desired (which the comment states that it is).