That is kinda...hmmm. Doesn't make sence. He could be giving you a "I want you outta my hair" answer. Remember, you are paying this guy money for a service. He should know this and with me being a non-certified architect, he should know better!
Sorry, he did want the 2 layer 5/8...then ledger. That make sence. I know it seems like you won't have enough support, but that is why you will have to send long lags into studs. So sorry, I blazed through the response and (I apologize) I was a bit hasty. Double 5/8 behind ledger is proper!