Hello
The documentation on website ydk.cisco.com is fairly old and pertained to YDK-0.8.3 and latest for that time IOS XR model, which is version 6.6.2. Actually, those "missing" nodes were introduced in release 6.6.3. The documentation for that release was not published.
If having API documentation is critical for your business, I suggest you to do the following:
git clone https://github.com/ygorelik/ydk-gen.git -b 0.8.5
cd ydk-gen
# this will generate, but not install the packages; just needed to generate documentation
./generate.py --bundle profiles/bundles/cisco-ios-xr_6_6_3.json
./generate.py --core --generate-doc
Note, that documentation generation (the last command) is going to take few hours and requires significant disk space, so plan this activity time and platform accordingly. After finished, you can display the documentation in your browser like this:
firefox gen-api/python/cisco_ios_xr-bundle/docs_expended/index.html &
Yan Gorelik
YDK Solutions