There may be bugs, but not hallucinations. Bugs are at least reproducible, and the source code of the verification tool is much, much smaller than an LLM, so has a much higher chance of its finite number of bugs to be found, whereas with an LLM it is probably impossible to remove all hallucinations.
To turn your question around: What if the compiler that compiles your LLM implementation “hallucinates”? That would be the closer parallel.
I think the idea is that you'd have two independently-develooed systems, one LLM decompiling the binary and the other LLM formally verifying. If the verifier disagrees with the decompiler you won't know which tool is right and which is wrong, but if they agree then you'll know the decompiled result is correct, since both tools are unlikely to hallucinate the same thing.
No, the idea is that the verifier is a human-written program, like the many formal-verification tools that already exist, not an LLM. There is zero reason to make this an LLM.
It makes sense to use LLMs for the decompilation and the proof generation, because both arguably require creativity, but a mere proof verifier requires zero creativity, only correctness.