>>236754
So basically FGO is a game where a bunch of characters are clearly be into you in various ways to various degrees. There are some that aren't, some that are married, some where most of their character is loving you, etc. but universally the MC is well liked and not treated as unimportant or really disliked, (You)'re always included in some way. An example is that Julius Ceasar is a thing with Cleopatra, but he just straight up offers to share her with you. This was the first consideration of "ML" and is generally more lax in its interpretation. The primary thing is the MC must be important to and cared for by most if not all characters in some form, but not all of them have to be romantic.
Later the chinks adopted it for use, particularly against Genshin since it went off the deep end and treated the player like an unimportant background character almost uninvolved with and ignored by the characters. They wanted to have the player be included and important to the characters, particularly romantically, so they used FGO as an example. It's important to note that it can be subtle, of differing types and not be overplayed, but characters definitely should not be shipped together at all. They stressed the romantic bit harder, so for this definition things like married characters sharing with you would not be their brand of ML at all. Wuwa is this kind. It does well by keeping out shippers and other annoying sorts like yurifags.
Usually it can get strawmanned by schizos like on halfchan into incredibly hyperspecific or weird, like insisting male side characters that appear for five seconds not talk to a female character, or that you're not allowed to have the option of a female MC. Be careful of those and just report them. Also try not to get into arguments about it since as the other anon said it derails the thread and only feeds trolls. Just ignore people and enjoy the game.