Now you're basically back to assuming the motives of fanfic writers and what they end up writing are completely different from anything that happens with IRL cis and trans gay couples. You're not going to know what sex is like for most of those couples because most people don't tell everyone the details of how they have sex. You just assume that their IRL sex is completely different from what fic writers write... and somehow you know this.
Well if we're honest, sex in fanfic usually isn't anything like sex IRL no matter who the characters are. And if someone does have trouble ever seeing PIV sex as not het, that's also honestly fair. But if you truly accept that trans men are men and don't want to be transphobic, that's the kind of thought you keep to yourself (and there's no judgment for that. Thoughtcrimes aren't real) including when it comes to fanfic. Including when it comes to thinking you know the people writing the fic are really trying to write het. All you need to do is ask people to tag their fic for non-canon trans characters, and not read that fic. None of that is transphobic. "Calling out" writers for writing stealth het by means of trans headcanons is. Even if that really is why they're doing it (spoiler: it's not.) You don't know. The only one who knows would be the writer, and as stated before, thoughtcrimes aren't real. Calling out writers for their alleged motives harms trans people more than the possibility that perhaps some of them are viewing what they write as het. If you're really concerned about the trans people reading the fic being triggered by dysphoria, again, that's what proper tags are for. So just focus on telling people to tag their fic and leave it.
Re: Secrets you don't want to make...
Well if we're honest, sex in fanfic usually isn't anything like sex IRL no matter who the characters are. And if someone does have trouble ever seeing PIV sex as not het, that's also honestly fair. But if you truly accept that trans men are men and don't want to be transphobic, that's the kind of thought you keep to yourself (and there's no judgment for that. Thoughtcrimes aren't real) including when it comes to fanfic. Including when it comes to thinking you know the people writing the fic are really trying to write het. All you need to do is ask people to tag their fic for non-canon trans characters, and not read that fic. None of that is transphobic. "Calling out" writers for writing stealth het by means of trans headcanons is. Even if that really is why they're doing it (spoiler: it's not.) You don't know. The only one who knows would be the writer, and as stated before, thoughtcrimes aren't real. Calling out writers for their alleged motives harms trans people more than the possibility that perhaps some of them are viewing what they write as het. If you're really concerned about the trans people reading the fic being triggered by dysphoria, again, that's what proper tags are for. So just focus on telling people to tag their fic and leave it.