I don't think the version with the math proof is meaningless in a probabilistic sense; my point is that the meaning comes from an additional factor unrelated to the dream, and I think Hobbes would agree that in the absence of any additional aspect of God speaking to the dreamer such as prophecies (objectively verifiable, like the proof!) there's no reason to believe him. But these additional aspects are the strange and unusual things which might oblige Hobbes to believe him, not the speech in a dream.