For Yuletide in particular the default assumption should be that they had no idea there was any fandom for this canon until they saw it in the noms list and would have no idea where to find it if it existed. Even if there's a few other fics on AO3 one can usually assume they were mostly written for other exchange prompts, or by a small friend group your recip isn't part of, or by an older fandom community that doesn't really exist anymore, not as part of an ongoing fandom with relevant norms.
If the recip writes a letter talking about the fanon they can counteract this a bit, but we're talking a blank signup situation. The canon is the prompt.
The situation might be a bit different if you prompted a large fandom. But this is yuletide. Even if you prompt a small fandom connected to a large one you're all supposed to assume nobody knows anything about the large one.
Re: Why isn't Yuletide growing?
For Yuletide in particular the default assumption should be that they had no idea there was any fandom for this canon until they saw it in the noms list and would have no idea where to find it if it existed. Even if there's a few other fics on AO3 one can usually assume they were mostly written for other exchange prompts, or by a small friend group your recip isn't part of, or by an older fandom community that doesn't really exist anymore, not as part of an ongoing fandom with relevant norms.
If the recip writes a letter talking about the fanon they can counteract this a bit, but we're talking a blank signup situation. The canon is the prompt.
The situation might be a bit different if you prompted a large fandom. But this is yuletide. Even if you prompt a small fandom connected to a large one you're all supposed to assume nobody knows anything about the large one.