Yes we do.
They are not redundant.
Let's look at usage guidance for all three tags:
Science fiction genre:
Used for questions on the science fiction genre itself, including its tropes and conventions. Should not be used to categorize questions about specific works of science fiction.
Used for questions on the fantasy genre itself, including its tropes and conventions. Should not be used to categorize questions about specific works of Fantasy.
Use this tag for questions about the history of the genre: the origin and evolution of ideas in speculative fiction. Example topics include the first work of speculative fiction with a particular property, or the origin of a term or trope.
It doesn't look like we can do without any of those three tags: each describes a specific area, and they aren't really interchangeable. One can (sure, why not?)
have a question about the science fiction genre without the
history-of tag, but it is not hard to see that
history-of adds a specific description of the question - that the question is interested in the history of the genre, not tropes or conventions (hard to draw a line, I admit).
On the other hand, purging the genre tags will certainly leave those ~200 questions orphaned - they will have history-of, but history of what? It looks to me like those three tags were specifically created to work together, and it looks like they're doing a good job.
Sure, there is always a chance that some of those questions are wrongly tagged, and in fact don't need some of the tags they have, but I find those sample sizes too large to be easily changed by a few mistags.
There's little chance they'll be used wrongly (I ocasionally see them in first post story-ID questions, but it's not a big deal) since they're no ambiguous - at least they have a tag excerpt that tells you where you do use them and where you don't.