As a retired controller I am out of the loop to some extent but I do believe that the FAA still prefers applicants with military experience. I was a controller in the Marine Corps and our standards were, at least stateside, closely monitored by FAA personnel. I respectfully refuse the “bad habits” argument above and the assertion that the FAA rejects military controllers. It doesn’t.
During my years in the FAA I observed hiring strategies come and go but the end result was, ultimately, a proficient, safety oriented and professional workforce. Controlling is a team sport and the proficiency of the person at the adjacent sector or facility can make your day at work heaven or hell. Controllers train their associates who make that day whatever it is so they are, as a rule, careful to weed out the marginal candidate.
Ability to perform ATC duties at the higher levels of volume and complexity is completely aptitude related. Just as some people can fly an airplane but can never grasp instrument flight, some controllers got it and some ain’t. As to who should have the opportunity to try, I believe the four day window to apply is not benefitting anybody but some HR wonk at FAA HQ.