It would be noted in the documents he signed. If he did not ask for information rights and it is not included in the documents he signed, you can just point him to the docs and say that given the docs and to be fair to others, you will not be providing these things. However, you’re happy to give him a general update in your next monthly update or hop on a call to give him an update.
That’s why having monthly updates for your investors is a good thing, puts everyone on the same playing field.