There was an older thread about the Everlasting Horn of Lavaswimming it looks like from a search: Everlast Horn of Lavaswimming - #10 by Mirasol-mannoroth
The community council person there got it without even knowing what it was, so doubt they’ll make their own thread in the community council forum sadly. They mention a higher chance being reported on wowhead on the first drop of the week, but with the time that’s passed and the additional comments now on wowhead, I now believe those wowhead comments were just anecdotal moments of luck and not indicative of how the drop rate really works. Just a few people who happened to get lucky on their first attempts in the week and posted about it.
If there was a boosted chance for the first in the week, it’d be pretty crazy that I’ve gotten something like 200 attempts in on “first tries of the week” across alts and still don’t have it, and I think many others are in the same camp. It seems to be just an incredibly tiny chance regardless of which attempt you’re on in the week. Though there was theorizing about whether there might be some “daily” lockout per character, I kind of doubt that’s the case too (though no one’s reported getting it on a character on later attempts on the same day of that character - I think partly it’s just that people get spooked so until they know for sure, they’ll not repeat attempts on the same alt if they have an alt who hasn’t attempted that day).
The thing that’s slightly more irritating about the current situation is that sitting in the background is the knowledge that if you DON’T get this thing during Dragonflight, even the pitifully tiny chance at getting it now will drop several orders of magnitude because of severe lack of participation minimizing the number of sieges that get complete, requiring more active participation rather than afk’ing and switching (which still takes time due to the need to monitor for quick alts switching) and there will be fewer server shards in general.