As far as my understanding goes, it's hardly possible to even verify that a compiled binary represents a faithfully executed representation of the source instructions, let alone that it will execute that way when run through a modern OS and CPU pipeline.
I would think the objective here is more about releasing server code that can be run independently in a way that 1) doesn't involve signal's infrastructure and 2) allows the client/server interactions to be audited in a way that trust of the server side is unnecessary, regardless of what code it may or may not be running.