As I said in the comments there, The Hugo Award is not just for science fiction, but for science fiction and fantasy, and it always has been, even when it was nominally the "Science Fiction Achievement Award." And, as a reminder, the Hugo Award's official name is "Hugo Award," as WSFS dropped "Science Fiction Achievement Award" as the official name in the 1990s. (One vestigial reference remains in the WSFS Constitution as a sop to people who were unhappy at WSFS officially recognizing reality.)
Addendum, 23:30: A comment elsewhere prompts me to clarify that the "recognizing reality" here means "recognizing that we were never going to be able to legally protect the excessively-generic 'Science Fiction Achievement Award' name and therefore we gave up trying to do so." Some people at the time -- I was there when the decision to drop SFAA as the official name was being debated -- didn't want to give up the name even though the US Patent & Trademark Office had turned down our service mark registration. It was not some sort of official recognition that "fantasy is now part of the Hugo Awards, although it wasn't in the past."