> Arguably defaults are always there, whether configurable or not. Thus you cannot claim to be familiar with an application unless you know how it behaves in its default configuration (whether that is in a GUI or a text file).

I don't agree with this part. The best way of learning about a program is to play with it. Knowing how a program is expected to behave is key, and without defaults you don't.

Even if someone knows the defaults, they will change.

(I agree with the rest of what you wrote)