There are 113 questions tagged plot-explanation.
It seems to be a meta tag (which as a concept is frowned upon on SE).
Used extremely inconsistently (113 Qs tagged; and I'm quite sure there are at least a thousand if not more on the site that are about plot explanation)
It doesn't seem to satisfy any of the purposes of tags
- Useless for statistics
- There are no "plot explanation" experts
- There seems to be zero reason to either search for "plot explanations" (since 25-50% of the site would fit that) or ignore them.