I think why he didn't flip just like Scarfo and why people like Gravano and Casso did is just what were they about LCN or themselves. Sure Scarfo was greedy and Gotti was a self serving egomaniac, they were gangsters to the core, they lived about cosa nostra. Gravano and Casso were gangsters as well but they more cared about themselves. They could of cared less about being seen as gangsters more so than just them doing what they wanted. Gravano was loyal but only because he was making a killing in construction and perfered the shadows, same with Casso. They didn't care about their images they only did what served them. Only a theory im proposing but it might come down to something as little as do they care about their image, or just care about themselves.