first of all, the way you worded this comes off as belittling, i dont know if that was your intention but thats how it feels. i'll answer regardless but know that i and anyone else with a nuanced identity are not obligated to to justify our identities to you because you dont understand it or at the very least respect our right to self determination. im going to be so honest with you when i say that sentiments like this in the queer community (as in "i dont understand your identity therefore it is bigoted to me personally/the rest of what i deem the 'real' community") is a deep plague to us. stupid ass discourse (which is almost exclusively an online phenomenon, btw) is not helping progress us as a community with ourselves or with non-queers, it isnt helping fight the often times life or death issues we face and it sures a hell isn't helping/uplifting anyone in our community; in fact i would argue it is doing the exact opposite of all those things.
anywho, on to answering your actual question. you clearly already know the literal definition of these terms but i feel your understanding of what being bi, pan, otherwise mspec, lesbian, gay, etc is incomplete (and i am not claiming mine or anyone else's is either, out of eight billion people it would impossible to understand every label as every individual sees themselves in relation to it). so let me just go over some things:
bi does not always mean attraction to two genders (often defined as two or more), it does not always mean attraction to both men and women (for example you could only like women and nonbinary people or any other combination of genders), and it is not always static attraction to the same two genders at a fixed preference (see the term bi-cycle, people who may or may not identify as abro/orientationally fluid may also identify as bi. not every bi person always likes two or more genders at the same time)
m-spec does not just mean bi, pan, omni, poly/poli/ply, abro. it is an UMBRELLA TERM for anyone who likes more than one gender. that can mean a lot of things to a lot of different people.
lesbian/gay/homo have not always meant exclusive attraction to the same/similar gender. lesbian started out as an umbrella term much like how sapphic is used now and gay started out as a derogatory term. in my opinion nothing about the term homosexual/romantic/etc indicates that it is exclusive, just that it is attraction of a same or similar gender or is queer in nature
heres a more tangible example of the labels being used like this: a bi lesbian who does not like men (likes women + nonbinary people, may or may not identify as enbian/diamoric/cenelian/etc), a genderfluid person who is only attracted to women so is sometimes hetero and sometimes lesbian (not inherently an mspec identity the way i described it), a multigender person who is homo- for both genders making them gaybian/sapphillean/etc (thats what i am!), a bi/abro/fluid person who always/commonly likes men and sometimes likes women might identify as bi/abro gay/straight, so on and so on. and thats not even getting into split attraction model (for example being bisexual homoromantic). are you starting to understand that conceptualizing queer labels as being rigid, "opposites" of each other and incapable overlapping is not reflective of people's experience with their identity and the way they chose to label it?
i feel like the reason behind some people understanding queerness like this goes back to recent gay rights movements which, while have been pretty affective and by far are a net positive, has "dumbed down" queer reality to make it easier for non-queers to understand. to make us more digestible, more conforming to "the norm" (which i have gripes with as it leaves many of behind, specifically those of us who cannot or dont want to conform to those norms). an unfortunate side effect of this is that now almost all queer representation in pop-culture is seen through this lense of digestibility, of respectability politics, which leads to even people in our own community (especially those who dont know an in person community and/or dont know queer history) understanding what we are and what we are capable of being as less than what it is.
if you'll notice mspec gays/lesbians/straights include both terms in the name, because the person in reference to the term is both. "why are you terrified of just being bisexual" i am just bisexual, i am also just lesbian, i am also just gay, i am also just something that no label will ever be able to fully describe. i like labels for myself though, they make me happy, so i stitch them together in a way that is me. do you understand yet? having a nuanced identity like this is not biphobic, homophobic or denying yourself what you are; it is quite the contrary, the labels i use were born from a deep love for myself, for how i experience identity. if you think being bisexual makes you "normal" thats your problem because i promise that is not the case. and ill say it! there are MANY ways relationships between a man and a woman can be queer (trans person with a trans person, trans person with a cis person (if that is how they see their relationship), transman/masc/etc in a lesbian relationship, transwoman/fem/etc in a gay relationship, aromantic or asexual spectrum, polyamory, male-female mspec relationships, and more). people seem to think that the label fits the person, the label controls what they experience, but that is not the case. all queer labels are opt-in, you choose them, that is the point. what they mean to the individual is extremely personal and unique to them. they are entirely subjective much like nearly everything else in life.
expand what you think it means to be queer, kill the cop in your head.
