There's a difference between knowing all the pieces that go into a working machine, and knowing how, in what order, to what end, and all the little interactions and knock-on effects in the form of of unwritten knowledge that keep a company cranking along.

Go ahead and set yourself up a Tomcat cluster, an internal Tomcat cluster, some Oracle databases, and even go so far as to reverse-engineer a UI and maybe a data model if we're being extra ambitious.

A business, you still will not have.

I'm not talking about a business perspective, I mean they're laying out their specific attack surface, zero social engineering required.