The human brain also doesn't full develop until 25-28 for most human adults.
The human brain largely stops developing grey matter (neurons) at about 11-12 yrs of age. What continues to develop until about age 21 and perhaps up to ages 25-28 is mylenation, which is the insulation of the neuronal axon with a fatty sheath to increase the speed of an electrochemical impulse down the neuron and across the synapse to another neuron. It is unclear if and how mylenation affects judgment during these ages.
The hype surrounding "brain development continues into age 30" is mostly that--a bunch of neuroscientists/psychiatrists that document changes in brain activity across different ages, including some new synapses forming in the frontal lobe in the late 20s. To me, calling these changes "development" is like calling a rusting roof with occasional repairs "development". It is likely that they are just changes in rewiring that co-occur age, but these changes don't necessarily mean it's still developing (likely the changes are just another form of brain plasticity, a hallmark of the brain).
I suspect that "good" judgment is not determined by brain changes (or "development") at age 25-28, but largely by other factors, most of which have to do with personality traits in combination with local circumstances and hormone levels. More importantly, the changes in the brain during the ages of 20-30 likely don't have anything to do with gender identity as this is clearly something that emerges early on, well before puberty.
