Everything on the internet has an IP address or nothing else could reach it.
And if that IP address is 10.30.100.10, it doesn't help you much.
and they don't have sufficient coordination to do an enter-exit attack
There is no exit involved in hidden services, so that attack does not help you much.
But if you want to believe that the FBI is stupid, ignorant and does not have authorization to investigate an online marketplace of hard drugs and that Silk Road will execute PDF scripts you upload to it and load images externally and is run by idiots and none other than you have any sort of understanding of how Tor works even if you
just learned that there is such a thing as hidden services, then go ahead, I guess.