its not the rape that triggers people. its the reaction to it. fictional rape and dubious consent can be hot, but the author simply ruined it here. the reason for it and the response to it.
But if they already know and SEEN the warning, they shouldn't be reading it in the first place if they were gonna react like this. Wether this is some kind of new consent thing, doesn't matter.
Like they said its not the rape its the reaction and response from the main couple is what triggers some people
People who cant get over the fact that fictional stories contain rape shouldn't be reading this