Good observations and some of this I also noticed.
I think a lot of pooner and female enbyism is about wanting to be "just a person" and not "put in a box"- they see that adult women and men are supposed to consider the needs of others, shoulder responsibilities, be a team player on whatever kind of teams, and they don't want anything to do that. They want to be a quirky uwu special little girl. They know they can't stay a little girl, so they try to become a genderblob instead. At least it isn't being a man or being a woman, both of which come with expectations and requirements (ie, being able to fulfill basic work duties and not be an asshole to your loved ones) that they don't feel up to.
To add to this: A lot of pooners already start out failing at some aspect of femininity. looks: they're fat, they're not pretty, they cant do their makeup or they were never taught to, they can't dress for shit, they are scared of the unsavorier aspects of being a woman like attention from creeps (common experience for most women), etc.
personality and/or behavior: they can't really grasp many social games women play with each other. an example from hoe math would be the whole "OMG GIRLS WE'RE ALL SUPER PRETTY PRINCESSES. TOTAL 10s!". They don't know girls never mean it when they call their fatter, uglier friend dressed like a drag queen wearing a choker for her non-existent neck "a 10" (and they will talk shit behind her back). They haven't been socialized enough to understand the complexity of social female dynamics. Some might not have caught onto the fact girls don't really... mean what they say. She doesn't want to know if you and chad are friends: she wants to know if you're interested in chad or if you two have already fucked. she doesn't care about where you got your bag, she wants to know how socially advantageous you are for her. she doesn't think "you're really prety!", she wants to know "oh, you THINK you're really pretty". And if you are pretty she just wants to keep you close because a beautiful woman/girl is not only a status symbol for men, but also for the women who are her friends (this mostly applies to a lot of young female social dynamics however).
I am not calling them tomboys because I find saying all TIFs are tomboys misses the point. Tomboys don't go out of their way to fuck with these rules and are their own person: Some pooners just failed at all or most of the things I mentioned above. They think, subconsciously, they can't be "women". keep up with the looks maintance expected of a woman, develop a subtler womanly perspective, and yes: social responsibilities and dynamics between men and women.
A lot of pooners, specially nowadays, arent the TIFs of old who were "tomboys" who were introduced to the concept of transgenderism early into their development or were victims of sexual violence who think, if they make themselves uglier and less womanly-looking (no breasts, no curves, no long hair, no makeup, body hair and ghastly beards), they'll dodge sex criminals. A lot of pooners, I've noticed, are just unfeminine (again, not saying tomboyish for a reason) girls and young women who would rather fuck out of womanhood because they're psychologically stunted, lazy, and could never bother to put in the effort (like trannies are just unmasculine guys who became the girlfriend).
I don't think they don't want to be put into a box: again, lots of girls and women SAY something they don't completely mean (she doesnt want to eat whatever, she wants you to guess correctly). They want to be put in a box of their choosing: the softboi aesthetic, vapor wave, cottagecore, or whatever will allow them to act like insufferable babies who can skip a shift because of their feelings the longest.
And it is important to mention that unlike trannies, TIFs have a fear of womanhood: they don't want to do what is expected of women: care for others, understand people's emotions, put effort into their looks because beauty is women's social resource and has been since THE FUCKING DAWN OF HUMANITY, etc.
They hold an infantile view of manhood too. they confuse men and women's differences and think "well men can do whatever!". no we cannot. we still have to care for others, we still have to be mindful, we have social responsibilities, emotional responsibilities to fulfill, and we're also expected to bring home the bacon. Their view of manhood is, in my opinion, the same one fast-food redpillers like faggot and almost baby daddy to a yacht girl, the pimp brotherhood, and mudshark cumdump with a fat fetish hold. Their view of manhood's not developed past: man want, man take, man fuck, man roid. In this aspect, as stupid as it might seem, them and pooners coincide. Pooners don't know what mature masculinity is because first: women don't know men's inner world and second of all, they are already stunted which means their idea of masculinity/femininity is still stuck at "they're a performance" instead of "they're a performance based on biological drives which affect our general behavior and that doesnt mean every man and woman is the same". They think that to be a woman is to become a brainless emotional thot because they don't know the value femininity holds that goes far-past the idea of "submission" or whatever.