>>3967884I'll break it down for you:
People who buy games often watch cute girls play games poorly, and even if they're spoiled, will still buy the game because the cute girl struggling effectively demonstrates the appeal of the gameplay enough for them to want to play it and experience it (properly) for themselves.
When someone who's good at videogames pounds their way through it, they exhaustively demonstrate everything the game has to offer. After watching someone like Astel or Botan play Village, there's nothing more you, personally can experience out of the game outside of niche NG+ stuff. They presented the game to you essentially as you would experience it. In essence, you didn't get a preview of the game, but rather experienced its entirety vicariously through them.
In all likelihood, the agreement with Capcom specified individual vtubers that aren't allowed to show endings, as a compromise. Capcom doesn't want good players to stream gameplay of their games, because it's less likely to 'sell' someone on it than watching a cute girl play badly. Cover doesn't want talents to be excluded from permissions. In the compromise, talents capcom identifies as being 'too good' to present the kind of gameplay that would 'sell' rather than obviate are instead restricted from spoiling the game's story conclusion, in the hopes that leaving the story unfinished will encourage their viewers to buy the game and experience for themselves.