It's possible that he can ignore the Office of Special Counsel. I'd guess that its aim is to deal with small-scale stuff like some branch acting improperly, not to overturn executive orders. Don't know, though. Probably have lawyers talking about it somewhere soon, if not already.
But I assume that if they've got a legal basis for a claim, this is just the first step before going to the courts.
investigates
Hmm. Apparently Trump ordered the head of the Office of Special Counsel, the place these guys are appealing to, to himself be fired, one Hampton Dellinger. Dellinger went to the courts and got a court order temporarily reinstating himself as head of the OSC. Apparently the Trump administration then appealed that reinstatement, and the appeals court refused to reverse it, and so the Trump administration is trying to appeal that to SCOTUS in Bessent v. Dellinger.
As a former manager, this is a hard fucking case to argue. Probationary periods are a way to delay cause requirements for firing. While firing a black worker for being black during a probationary period is absolutely illegal, most other causes are ignored and the documentation is a lot easier.
During the probationary period the employee is waving significant rights so this law team will have a very high burden of proof for their arguments.
This is just hearsay from another federal employee, but word is they were terminated for performance issues (that almost certainly did not exist). I'm not sure if that makes a difference, but thought I would share it.