Sorry, Kevin, you may want to re-read the proposal which is actually very explicit about the points you bring up. It would be folly to ask anybody (but the nominating fans themselves) to distinguish between F and SF. While the suggestion is mostly tongue-in-cheek, it is certainly within the perview of the WSFS to decide, if it wants, to state the theme of the awards. It probably would not want to, people are clearly voting for the fantasy.

The award certainly has a theme. While voters could nominate non-F&SF if they wished to, and the administrators would probably obey them, they don't. They don't because they have that theme. Definitions are not needed nor are they a great idea.

As for the worldcon, I'll be back next year after missing the last few years due to Burning Man and (in this year's case) travel logistics.