This FHA requirement has been around a LONG TIME. The fact your LO doesn’t know about it describes his lack of experience as a Loan Officer. He should have advised you at prequalification stage about this requirement.
The only thing to do is keep your Seller “in the loop” keep communicating and sit tight until you have your 30 days of paystubs in hand. You’ll probably need to update your bank statement to the current month, too, depending on the Lender’s requirements.
Sorry you had to find out “after the fact.” There’s too much of that going around in the mortgage biz.
Trevor Curran NMLS #40140