most gender benders tend to be f/f for three reasons, which are very different but one of them is always the case.
1. the Author wants to write a lesbian harem cuz its hot, but doesnt want to actually write about lesbians cuz "muh gay people" so they pass it off as really being straight cuz MC is "actually a guy" .... this tends to be more common in chinese genderbenders but i have see a few on SH and RR.
2. the author is a lesbian. self explanatory really, they write their own experiences.
3. the author thinks genderbender where the MC becomes a girl and ends up liking guys is "comphet" or "compelled heterosexuality" .. they dont like the thought that peoples sexuality changes to be straight because of their gender. which in my experience, half the comphet claims are actually assumptions. like ive seen novels where the MCs sexuality was never once mentioned but the moment he (now she) ends up falling for guys people drop it for 'comphet' which ..... just means they ASSUMED the MC was straight, when it was never said that they were. which isnt really a good thing to do. authors who dislike comphet will sometimes end up doing the reverse in revenge and have their gay man MC end up liking girls when his gender changes so that he remains gay/lesbian. and tbh thats equally as bad.
anyway, its why i skip a lot of the GB novels on SH even though i really like GB novels: its 90% girls love, and tbh I'll even take no romance over girls love, its just oversaturated and as im not a lesbian myself (trans het) i just cant relate. its the same issue with the oversaturation of fox girls. like even when given a choice by the author between really cool arachne girls and such, the readers *always* choose foxgirls, and frankly it gets pretty old
This is kajarainbow signing in an alternative account because for some reason the forums won't recognize my main account. This is my first time using the forums.
I doubt 3 is quite as common as you think but comphet is a real issue in some stories, where the MC is forced to like guys even if they liked girls exclusively before. I've seen stories that used female hormones or otherwise being in a female body as an excuse when lesbians do exist. It's one thing if it's a process of discovery where it's a transgender girl who realizes she liked guys all along, quite another if it's an actual change in their preferences because of the transformation. In general stories where the MC experience mental changes such as becoming more stereotypically feminine or changing their orientation are essentially mind control and should be labeled as such while stories where they realize that they liked those things all along are not mind control.
For authors who don't want to unintentionally write a mind control story but want to write a genderbender story, here are my recommendations.
Option one: make the MC transgender all along. In other words, they get changed in a line more in tune with their true self and are happy about it. It might take them a while to realize why they're so happy about it. If you go this route and aren't transgender, I recommend consulting with someone who is. I don't mind people contacting me for this. Likewise if you want to have them like guys, make them like guys all along, they just were afraid of admitting it or were hiding it or something.
Option two, just make the MC flexible. They were fine with a masculine body and are fine with their now feminine body. This doesn't mean that you can't write them getting used to their new body, suddenly switching to a different body is a weird experience after all. But just have their overall attitude be something like "this is weird but ultimately doesn't bother me that much" or "yeah whatever shrug" or something. Likewise for sexual attractions, just make them bi all along and hook up them with a guy or whatever.
Option three, have them hate it. Hate their body, hate the expectations others put upon them just hate everything associated with the change and actively seek to change back. This is both rough to write and rough to read but it's a legit option, just hard to pull off in a fun way if you're just looking to write a fun story.
Note that the MC's interests won't change just because they are in a new body. If they liked working on cars, they'll still like working on cars. But they might feel more comfortable pursuing interests they had all along but were afraid of people judging them for, like doll-making. Likewise, they might get pulled by someone else into a new hobby and realize they like it.
Likewise with cloth styles, they might stay with their old style with just some small adjustments for their body's new dimensions, like adding a bra underneath their polo shirt. Or they might wear things they wanted to wear but were afraid to. Or discover that skirts are actually comfy and add some into their wardrobe. Or they might be the sort to go with the flow and wear whatever others pick out for them.
My point is that organic changes are fine but abrupt ones can come off as mind control.
Unfortunately transhet is a minority and I wish there were more of us! 
