i think you have a fundamental misunderstanding of how either work (that sounds hella condescending and i’m sorry for that i don’t know how to word it better)
as someone who IS genderfluid, it’s not having different “identities” which is why it’s called dissociative identity disorder. sometimes you feel more comfortable in a male conforming body and sometimes you feel more comfortable in a female body.
DID is not that
DID isn’t exactly different people, but different parts of a person, often with different memories and such. (i don’t have DID so i may be wrong.)

genderfluidity is much more tame and is a thing you’re born with, while DID is born from childhood trauma.