Note that discrimination based on age generally only applies to applicants 40 or older. For example, companies can restrict hiring to people over 18 (e.g. to sell cigarettes), over 21 (to sell alcohol), over 35 (to be president) but they cannot say no applicants over 50.
These laws protect you against employment discrimination when it involves:
Unfair treatment because of your race, color, religion, sex (including gender identity, sexual orientation, and pregnancy), national origin, age (40 or older), disability or genetic information.
And they even note that they are a proud equal opportunity employer and don't discriminate based on age. The fact is they will hire older people, just not as special agents. Special agents have a mandatory retirement age of 57 so anyone older than 37 will not be able to work 20 years (required for government penaion). I'm not sure if a private sector employer could get away with that.
That doesn't seem to align with job functions (education, training, writing/editing) and the fact that they're recruiting tenured university professors for this job.
And "almost military" doesn't mean military; military is exempt from ADEA, but FBI, in general, is not.
Maybe someone copy-pasted key requirements from an army-type position for this desk/teaching job, but even then they explicitly say at the bottom that they don't discriminate based on age.
These laws protect you against employment discrimination when it involves:
Unfair treatment because of your race, color, religion, sex (including gender identity, sexual orientation, and pregnancy), national origin, age (40 or older), disability or genetic information.
https://www.eeoc.gov/federal/fed_employees/index.cfm