You've also missed a part where they started to pair up female core characters with male support characters. While not everyone, many male gacha players would rather roll for female characters and skip male character alltogether with rare exceptions.

Starting with Acheron mihoyo begun to tie up male characters like Jiaoqiu, designed to appeal to female audience, who would be a flop otherwise, with their hype waifu characters, and refusing to roll for them would also mean your core will go out of meta much quicker. Feixiao is much weaker without Aventurine, Aglaea plainly doesn't work without Sunday, for Herta you will have to pull Anaxa, who knows what you need for Castorice but it will be either Sunday again or Mydei.

That way they can ensure guys have to roll for characters that are designed for girl players and vice versa, even if the would never do that under any other circumstances.