I did receive a reply -- that "the “siblings” you see mentioned in code refer to documents in the same folder as one another in Google Drive. Links to sibling docs should show up in a box at the bottom of any document or folder page."
And thanks for confirming that it does what I was thinking.
But I wanted to further point out that this functionality isn't working for our site. And from what I can see in the github repo for the project, I think this code has been commented out:
Hoping someone could explain why if the functionality is supposed to be in production. Or perhaps explain what other types of pages there are other than "normal" ones -- perhaps I need to do something to trigger its usage?
Cheers,
Dan