I'm not sure that I understand the confusion. "Person" is defined differently ALL THE TIME.
For instance, a "person" in the US has a right to vote - provided that this "person" is a US citizen. But, a "person" in the US can also be prohibited from voting - if they are a felon or illegal alien.
"Person" is like "thing". Just because a table is a "thing", doesn't mean that an aardvark also isn't a "thing".
A "person" can be a man or a woman, both of whom have all sorts of different rights from each other (a man is forbidden from entering a women's bathroom, for instance). And, a person can be a corporation, but has different definitions, rights and privileges.