That's what's covered by the "assuming you have formalized the statement correctly" parenthetical.
Given a formal statement of what you want, Lean can validate that the steps in a (tedious) machine-readable purported proof are valid and imply the result from accepted axioms. This is not AI, but a tiny, well reviewed kernel that only accepts correct formal logic arguments.
So, if you have a formal statement that you've verified to represent what you are interested in by some other means, Lean can tell you whether the proof created by genAI is correct. Basically, there is a nigh infallible checker that won't accept incorrect hallucinations.
It depends on whether you are doing something security critical with the result.
Maybe you have a trusted table hash but only a user-supplied version of the table. Before you use that data for security sensitive queries, you should verify it hasn't been modified.
Basically, if you ever have to contend with a malicious adversary, things are more interesting as usual. If not, addition is likely fine (though 2^k copies of a row now leave the k lowest bits unchanged).
XOR is not a great choice here. Consider that 2 copies of a row give the same result as 0 (or 4, 6, etc). And even without multiple copies of rows, you can force any hash you'd like by observing what happens when you insert more random rows
and finding a subcollection that flips exactly the bits you want.
What you probably want to look at is homomorphic hashing. This is usually implemented by hashing each row to an element of an appropriate abelian group and then using the group operation to combine them.
With suitable choice of group, this hash can have cryptographic strength. Some interesting choices here are lattices (LtHash), elliptic curves (ECMH), multiplicative groups (MuHash).
Given a formal statement of what you want, Lean can validate that the steps in a (tedious) machine-readable purported proof are valid and imply the result from accepted axioms. This is not AI, but a tiny, well reviewed kernel that only accepts correct formal logic arguments.
So, if you have a formal statement that you've verified to represent what you are interested in by some other means, Lean can tell you whether the proof created by genAI is correct. Basically, there is a nigh infallible checker that won't accept incorrect hallucinations.