Is "obscure" the same as "undocumented"?

No. Obscure here means "of little or no prominence, note, fame, or distinction".

Documented might only mean written down. It might be written in an obscure place.

However, the point made by your fellow community member still holds; he just didn't say everything he meant as well as he possibly could. He could have used a word like well-documented to press his point more convincingly. His main point was that the info you need is out there to be found.

To summarize: you can't hyper-analyze comments.

Obscure is not the same as undocumented.

Here's an example, in a similar context as the question, though not specific to a programming language. The Internet Engineering Task Force (IETF) memos are full of obscure information, e.g. this specification that defines the protocol referred to as HTTP. Much of that text could be considered obscure at this point in time. Yet it is one of the cornerstones of the internet. It is a very well-documented standard.