The LinkedIn Developer documentation states that full profile information is only accessible when calling the "Apply with LinkedIn" API.
But in practice, when doing a simple test using my own LinkedIn profile I manage to access the Full Profile fields via a "Sign in with LinkedIn" call (I use the JavaScript SDK btw).
That's all very nice because it means that I can access more fields than I expected via the "Sign in with LinkedIn" API, but isn't that a security bug?
PS: If you're a LinkedIn developer, there is a typo error on the Basic Profile fields page: field specialities should be spelled specialties.
@JustinKominar's comment is the answer:
There is a blog post (https://developer.linkedin.com/blog/posts/2015/developer-program-changes) that explains that the recently announced changes to LinkedIn's API program will take effect on May 12th, 2015. You still have access because we are still in the transition period between the announcement and formal change. Presently, all previously documented capabilities are still available to you.