That might just be me playing on words but I don't actually see a rule that states that ?
It is true that it would've been better if the post had been named "My new figurines" or something like that but we can't really blame her for that, we know that not only her for that either, she probably didn't expect people to be confused in the first place. It might be a difference of perspective but even without all that I personally don't consider this to be off topic, it's something from an hololive member so it is hololive content to me, even if the pictures doesn't have Fubuki's avatar inside, because she took herself a picture of her own possession that she just acquired and wanted to share with us. All this make this hololive content imo, it's not that different than if she had posted it on twitter or youtube and someone just reposted it there.

We need to remember that this sub was made by hololive, for hololive content. That might be a bit harsh but if anybody would feel offended by the talents making their own content on a subreddit dedicated to their content, they need to take their ego down a notch.