So we closed over two weeks ago, the attorney is saying the lender forgot to add the 1-4 family rider, and want us to initial it as an addendum.. any thoughts?

Hypothetically, the property may or may not be student housing, and may or may not have more than 4 'families' 

Would this impact my insurance at all? Are there any advantages or disadvantages to agreeing to sign?

I'm obviously not planning to default so I don't think it would ever be an issue anyway, but just hesitant to sign something after the fact.