Bluespoet seems as confused as you were about FCS and how the suite integrates. He doesn't make it clear if he's actually used FCS. One explanation is that he's used a pirated copy of FCP as a standalone, I know from some posts here that there was such a thing in use a while back.
Anyone using a modern-legit version of FCS would have Soundtrack Pro and that's where you do the complex audio work.

Vegas is better at digital video
Yeah, so you keep saying. But it's all digital video, what other kind is there, analog?