Before writing this article, I checked on what "probationary" means for a federal worker. I've gone back to that source, and will quote from it:

"5. Do probationary employees have civil service protections? Not fully. Probationary employees do not have the same level of protection as tenured federal employees. This means they have limited rights to appeal removals or disciplinary actions."

"6. Can I be removed from federal service during my probationary period? Yes, a federal agency can terminate a probationary employee with comparatively little process."

"7. Do I have appeal rights if I am terminated? The Merit Systems Protection Board (MSPB), which hears most federal employee termination appeals, does not typically have jurisdiction over appeals from probationary employees. However, under 5 C.F.R. § 315.806, probationary employees may appeal their removal to the MSPB if they allege it was based on partisan political reasons or marital status, or that certain procedural rights were violated. "

I interpreted all this to mean that "probationary workers typically [have to] work hard to convince their employers that they should keep their jobs." Though I did use the word "trial," the word does seem to me to apply. But I do understand your interpretation of it as well.

Do you have some personal experience with this or knowledge of it that would help both of us understand the situation better?

I do like to get all the details right.