"V-coded at age 5 privilege" is a phrase which is stuck in my head.
There is often the attitude that we don't "become" our gender until we've been through medical transition.
Some trans people exaggerate and exacerbate this by saying they "literally" changed sex in the process.
But what we are as children is nebulous unless we jump and down begging to be taken seriously. And sometimes not even then unless we're lucky enough to transition that young.
Otherwise we were neither girls nor boys but some secret third thing which people don't want to think about.
Is it guilt or complicity they're uncomfortable with? The idea that girls and boys are harmed every day by having their selves invalidated?
Or are they still ultimately just squeamish about "the trans question" and whether we're valid at all?
Watching the hysteria surrounding trans kids and trans girls specifically playing sports, it feels like most people, even ostensible allies, still fall on the side of "you're not REALLY a girl, though."
And I would go through all the ways trans girls are abused, bullied, and sexually assaulted growing up, whether they Always Knew (TM) or not, whether they're legibly female or not, in part because male social groups organize a hierarchy in which the least powerful, least masculine are rendered into effective "girl" status, even irrespective of being cis or trans or gender nonconforming, and how that automatically makes them a target for such violence.
But it doesn't seem to make a difference.
People are often iffy about trans identities. Even allies often adopt the posture of supporting our access to healthcare and our right to live our lives in a way that makes us happy, while remaining largely silent on the issue of whether we are our genders.