No, probationary federal employees cannot be fired for any reason. They have protections, and can challenge firings that violate their rights.
Explanation
Probationary employees can be fired for poor performance or conduct.
They can be fired if they don't demonstrate that they are fit for the job.
They can't be fired for discrimination based on race, gender, or disability.
Whistleblowers who report fraud or abuse are protected from retaliation.
If a probationary employee is reinstated after a successful legal challenge, they may be entitled to back pay.