In the wikis for several Umamusume characters, there are listings of the IRL horse's relationships. For example, their mates, children, etcetera. This is fine. These sorts of listings could help users understand certain jokes that no doubt come up in fanworks. But for some inexplicable reason some of these relationships are in spoiler tags? (Maruzensky, Daiwa Scarlet)
I am not a Umamusume fan. I know nothing about the series. So what I'm wondering if this is something important within the fandom? Like... something about protecting the sanctity of the horses? Any explanation would be much appreciated.