You might as well say all humans have a soul. Or that all humans believe in God.
Or that all humans have a flibble identity, a sense of who they are in terms of flibble.
Flibble either being undefined, or somehow associated with a physical attribute, like, say, height.
You could rebuild the entirety of gender identity ideology using flibble+height instead of gender+sex. Would work just the same.
Could even have neo-flibbles. Boring cis-flibble people might have flibbles like 5'10", but really radical transflibble people could have flibbles like 125mph. No need for neo-flibbles to be constrained by cisnormative units of length.