Nasser, Coleman, Gunter all had masssive guts when not posing. I have no idea what you're talking about...
Coleman didn't develop a gut until the 2000s. And so did Gunter. Gunter was 290 pounds at his first Mr. O, and no gut. Nasser at 260ish pretty much lacked a gut.
But, one who you'd think wouldn't have a gut, but did, was Flex Wheeler. Look at his Mass Construction vid, which was after the Mr. O contest. There is a part where Danny Hester is pulling Flex's arms behind his back, and Flex loses control of his gut.