Agreed, this is incredible - especially to have something that can be perused in physical format.

Looking through some of the examples for the languages I know well enough to judge, these seem to be good quality. As a simple case in point, for how to open a file in Python they only show using a context manager. Even though you can easily read files without that, it is the better, safer, perhaps slightly-more-intermediate-level option and also makes a person more familiar with context managers in general. So it is nice to see best practices presented as the defaults.