The language syntax may be the same, but programming approaches might be very different. I've seen parts of a Smalltalk program where it was coded like spaghetti copy-paste Fortran, and it's actually hopeless to try and fully understand the semantics and still meet your deadline. But I was able to use a few tricks to prove that certain modifications wouldn't alter other functionality so I could get my work done. In the same program, there was well factored code with a nice object model, where it would behoove you to understand the part you're working on in a more conventional way.

On reflection, I think you may be right that good code is good code. Size of the system matters most when the code is bad.