For completeness, the whitepaper is here: http://matasano.com/research/bypassing_openssl_pinning.pdf
I was super confused what they were talking about, until I remembered that "penetration testing" really just means "penetration", not "testing", it's just a euphemism for "attacking". I think?
I think, there is two things to that.
First, for dynamic C/C++ libraries like OpenSSL, some degree of symbols have to be maintained in order to relocate the library and find the entry point to the corresponding function.
Second, Objective-C is a dynamic language and as such the binary will always include the Objective-C method names. The reason is that they are resolved at runtime (via so-called "selectors"). In fact, Objective-C doesn't technically call methods but they use a message passing system. So if you pull any app from the app store, you can determine all classes, methods, and mostly arguments of the methods.
