>requires signing an NDA and spending anywhere from a few hundred to to a few thousand for a development kit.

>Some of this is because the manufacturer considers the information to be proprietary and also because they not setup to support large numbers design teams

No, it is what is called a pain sales tactic. You make a person to go through big pain, spend lots of resources just to get a devkit, so they would not be inclined to throw it out midproject because it sucks