Something weird here, why is it so hard to have a deterministic program capable of checking a proof or anything math related, aren't maths super deterministic when natural language is not. From first principles, it should be possible to do this without a llm verifier.
Maths can be super deterministic but often difficult to compute because of concepts like inferring by induction. I had to personally unlearn and rebase my understanding of math based in computation to 'get' pure maths. Another example is set building. You often don't need to compute the existence of members of sets in pure math you just need to agree that there are some members of a set that meet the criteria. How many or how many things that aren't in the set aren't meaningful often times to accept something and move on with the proof. From the computing perspective this can be difficult to put together.