straight person vs someone

straight person and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
straight person	Yes	No	No	No
someone	Yes	No	No	No

As nouns, someone is a hypernym of straight person; that is, someone is a word with a broader meaning than straight person:

straight person: a person having a sexual orientation to persons of the opposite sex
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of straight person include individual, mortal, person, somebody, soul.

straight person (noun)	someone (noun)
a person having a sexual orientation to persons of the opposite sex	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential