1. Non-genrealozable: soldier is a unique overriding identity, military is immensely controlled and regimented co,parked to irl, selection bias for similar people anyway (more blacks were removed due to testing after all)
 
2. The military was very white and still is. Especially the leadership. So conformity is in effect and demographic blindness is not warranted
 
3. Differences still persist despite all the positives of social contact
 
4. Outside the military it amounts to "people with friends of C group like c group more" which reflects a voluntary selection effect. See mandatory diversity training for it not being generalizable