It isn't. If one accepts the premise that gender is separate from biological sex, one accepts chosen gender-based pronouns as acceptable descriptors of a person's gender identity, but the premise of gender-based pronouns is that they describe gender. As the set of human genders is not infinite, the set of valid pronouns to describe human gender is also not infinite.

"I identify as an attack helicopter" is obviously stated in bad faith, as "attack helecopter" is not a valid human gender. "God" or a base64 hash are also obviously not valid genders. The only people who would do so to begin with are trolls who want to mock trans identity.