As far as I know, pyvmomi is not deprecated. It is also used internally by VMware or in HCI solutions for certain tasks.
The second link to the Github documentation contains API examples and documentation. But since versions 6.5 and 6.7 the API of vCenter and other products has changed to better unify them.
And apparently they no longer want to maintain this in the Github documentation, but now refer directly to the official API documentation at code.vmware.com.