I can't seem to find an answer to this anywhere, so I thought I'd check here. I'm booking a 4 night stay at a Sheraton with a club lounge using the Citi Prestige concierge and the 4th night free benefit. I'm wondering if I still get lounge access with my SPG business Amex? Some research tells me that booking with 3rd party sites like Priceline and Expedia do not get the lounge benefit of the SPG Amex. What I can't figure out is if using the Citi Prestige concierge falls into the third party booking category.

Thanks!