How are they disambiguating between these brain markers being an effect, or a cause, of being an F16 fighter pilot?

Like claiming "Becoming an Olympic swimmer causes long torsos, long arms and short legs"

They should at least have control group be students in flight school, and then throw out control subjects that don't graduate. Of course, better would be before and after flight hours for same people. Seems pretty obviously flawed to just compare to some random other group of non pilots.