I just got the Dungeons & Dragons 5th Edition SRD from this webpage at Wotc. At first, I found it interesting that several of the sub-races were missing (I assumed something happened with them not being Open Content) but then I found something else: on page 28, there's a reference to three monastic traditions, and only one is actually listed in the text. The same thing seems to be happening in many (if not all) of the other option groups.
Is this an actual error, or is it that not all the options are Open Content per the OGL?