No, they're doing it to probationary employees because they're aren't protected by the same laws that require cause for firing.

Political appointees require 30 days notice, rank-and-file must be given cause.

Yeah. They have less protection, less political power to resist. They also presumably generally aren't running important things and filled with tribal knowledge so at least in the short term they are more disposable (if you don't care about the future)

I don't mean that - I mean it's unlikely you can have people on probation stay on while making other people redundant, just from the perspective of regulations or union rules around redundancy.