While I agree that nobody who says "my gender is attack helicopter" actually believes it, the idea of the statement is that 'merely saying you are x does not mean you are x'.
But why not? Indeed, most sociological race theorists contend that race is entirely socially constructed; that there's even less, biologically speaking, to race, than there is to sex. So if somebody can declare they are a gender that conflicts with their underlying sex and we should accept that, how much the less can we then object to somebody stating something about their race that has no underlying biological conflict?
A feminist philosophy professor made an argument that we should accept transracial people in the same way we accept transgender people and for the same reasons. The article was published in a philosophy magazine.
The reaction was swift and deeply hostile. The article was withdrawn, the editors resigned and the magazine made craven apologies. The same feminists who think TERFs should be put on a pyre could not tolerate a well-argued position consistent with their premises but conflicting with their beliefs.
In the best of worlds, a world where racist proxies were no longer used against people like a cudgel, I would wholely argue that trans-racial identities be accepted, and that people be allowed to freely take up cultural models, mix them, and synthesize new culture from the old.
In today's world, though, there are issues with doing so because racial culture is imparted through shared trauma.
It would, to me, be similar to someone claiming to identify as a soldier having never fought in a war or conflict, never having training or experiences that actually create what I would charactarize as a soldier. If you have not shed blood in the mud, I object to your appropriation of the label.
As such, because racial identity is sadly, in today's world, a product of getting ground up through the gauntlet of racism, it is not something that someone can rightfully transition into without also taking on the traits and experiences that such an identity is predicated upon.