The existing functionality currently disables both the parent and its child nodes, but it is necessary to disable only the parent while still permitting the selection of the child nodes.
The current workaround relies on a template and using custom CSS which isn't practical, but it is a working option:
https://stackblitz.com/edit/angular-2ricmg?file=src%2Fapp%2Fapp.component.ts
Current behavior:
All parent items are available for selection unless they are disabled.
Expected behavior:
Items that are parents should have a third state that allows them to be expanded but not selected.
In many real-world use cases, parents are categories that are not supposed to be selected and only exist to categorize the child options.