Personally I think that there should be more of an upfront acknowledgement/warning about themses of sexual assault specifically since even in a mature rated game, it's not and should not be a given that sexual assault will make an appearance. Having a warning pop up in the middle of the game? I'm less certain on that but I personally would not be against it. Honestly I'm a big supporter of including trigger warnings and if they were included I'd never be against them, just on principle if nothing else. I also think that in general, if you need a trigger warning for certain things, you KNOW you need a trigger warning. So the opinion of the average player who knows they don't need one should probably be weighted a touch lighter. Trigger warnings aren't just about being uncomfortable, they're specifically about ptsd and I don't feel like the general public should be the dominant voice in discussion with regard to that.
As for the point someone brought up abouthow other media doesn't have trigger warnings, I think games are kind of unique in that they're so much longer than any other form of media and so they can fit in things that might not be implicitly part of the premise. For example I wouldn't go into this game assuming sexual assault would come up, whereas In a book or novel when you know the premise, you can pretty reliably know what could be included. Frankly I wouldn't be against trigger warnings being included a bit more liberally in other media. I think the most important thing though is to have them up-front so people know what they're getting into and can refund/not buy to begin with. I myself am speaking as someone who hates horror and never watches it, and is probably too sensitive. I once saw a description of the plot of a horror movie on youtube and it haunted me for weeks after. Same with reading the TV tropes page for that movie Us. So that's the constitution of the person making this argument.
Relatedly, I consistently see way more people arguing against trigger warning than I ever see arguing for them, and that makes me... uneasy for whatever reason. LIke, I don't know that I've ever actually seen someone online argue for trigger warnings on stuff, I just know it's an argument that broadly exists.