The reason I am very confident about this is that there is a very long and boring history of law on federal employment.
The pattern is not an ideological one—it is that the courts do not want to get involved in federal personnel issues.
The statutes created one separate body for individual complaints, another body for union issues.
The Supreme Court has blessed that arrangement in the past.
More importantly they love it.
They do not want to get involved in this stuff.
They will wave the “standing” flag and then go home and relax.